Ramp Controller reported push back error due to confusion between push boxes resulted in ground conflict.

Narrative

I was working lunch relief shift. At XA:19 I was covering H alley ramp control for 15min break from XA:20 till XA:37. Relieved ramp controller advised inbound aircraft holding on the pad for X5. No movement in the alley. Gate X8 schedule departure XA:25 request push at XA:21. HX push was approved at XA:21 aircraft pushed at XA:21:18. X8 push to east taxi line complete XA:23:18. X14 schedule departure XA:30 request push XA:25 and approved for push. X14 pushed XA:25:33 to the east taxi line. X14 push complete at XA:27:00. X14 request taxi XA:28 approved out East taxi line aircraft taxied at XA:28:29. X8 request taxi XA:29 approved taxi out east line at XA:29 aircraft moved XA:29:15 number two in sequence on the east taxi line of the H alley. X4 schedule departure XA:30 request push XA:29 and approved. X4 pushed XA:29:38 on to the east taxi line; tail south. X10 schedule departure XA:35 request push XA:29 held for taxi traffic off X8. X8 cleared east taxi line behind X10 at XA:30:25. Y5 request push and approved XA:30.Y5 pushed at XA:31:01 to the west taxi line complete at XA:31:53. X10 push approved XA:31:07. I stopped X10 push at XA:31:45 when I realized lack of clearance for the push with aircraft off X4 in push back. X10 stopped on the push line just at the start of the turn off X10. X4 push was not stopped and was complete on the white box a beam gate X6 at XA:32:07. Y11 request push XA:33 and approved. Y11 push to west line complete XA:33:40. Y11 taxied at XA:36:35 number one on the west line. Y5 taxi at XA:36:09 number two in sequence on the west line. Aircraft X4 taxi approved XA:36:39 in sequence number three on the west line. [Relieved ramp controller] returned from break at XA:37 I advised X10 push was held and to resume push once aircraft off X4 taxi to west line. X10 resumed push at XA:37:02.As I monitored the push off X4 to the east line tail south and saw pushing past red box; I immediately stopped the push on X10. Aircraft was still on the X10 taxi line and had just started the turn. I apologized for the stop and advised will resume shortly; explaining I had observed there will not be enough room with the push off X4. I turned to my co-worker; the turn coordinator for zone 3 (gates X18; X16; X14; X12; X10; X8; X6; X5; X4); I advised I stopped the X10 push in case ramp control called asking questions. I advised of the alley traffic and plan to continue the push after aircraft X4 taxi to the west line.X bottom of the east line of the alley has two push boxes one red between X4 & X5 gates; one white box for main line between X5 & X6. My shift assigned lunch relief to cover all breaks for ramp control and turn coordinators on shift. I work from my position relieving each employee for their assigned breaks. I had just relieved H ramp control for [their] 15 minute break at XA:19. Relieved ramp controller advised inbound aircraft holding on the pad for Y5. No movement in the alley. I was on leave of absence for X days for covid-19 illness. No idea why I mixed up the red box for the push point for main line from X4 & X5 pushes; but I did. When I approved the push for X10; my vision was X4 was pushing with nose on red box lower in the alley than the white box on the east line.I managed the X alley ramp traffic and took safe actions to correct my error. No aircraft made contact; no ramp fleet service employees were outside the X10 taxi area. As the events unfolded my manager asked why I thought there was clearance to push X4 & X10 mainline aircraft. I advised I confused the white and red push boxes on the east line. Apologized for my confusion and advised I stopped the X10 aircraft from completing the push to the east line; and will continue the push after I clear the alley traffic. Not to confuse the push boxes on the east line of the X alley. Working as lunch relief there is no time to pre-plan departure pushes. I have to react; pick up where my college was working to relieve them on breaks.