B757 Captain reported after leveling off in cruise; they got a master warning and cabin altitude indication. While descending to destination airport flight crew determined cabin altitude control knob was not in correct position.

Narrative

Flight XXXX was a maintenance reposition flight from ZZZ-ZZZ1. This was our second flight of the day after bringing another aircraft in from ZZZ2. The aircraft was ready when we showed up to ZZZ and we started to get everything set up. The preflight was more complicated than usual due to lack of satcom and ACARS. This increased the workload to get the aircraft off the ground. Several switches in the cockpit were not in the 'normal' position due to Maintenance operations at ZZZ. Once in flight we were at FL300 for about 1:30hr when we started to encounter some light to moderate turbulence. There were also weather build ups ahead so I requested higher for a possible smoother ride. ATC cleared us to FL360 but asked that we climb at .77 Mach. Once we leveled off; it was smooth for about 15 minutes and then we got the Master Warning and Cabin Altitude lights. I glanced up at the Pressurization panel and saw the Cabin Altitude indicator was between 10 and 15. I then reached for the Oxygen mask and the FO did the same. Once we got the Masks on; we turned up our speakers and I reached for the QRC and handed it to my FO. I said I have the aircraft and for him to run the QRC for CABIN Altitude. The FO ran through the first 5 items of the checklist and with the CABIN ALTITUDE light still illuminated I decided to advise ATC of the issue and request descent to 10;000'. ATC cleared us to descent and I started down. The FO followed through the remainder of the checklist and we continued descending to 10k. Once level at 10k; we took off the masks and advised ATC of our 2 SOB and 1:40 FOB remaining. I sent an ACARS message to Dispatch and advised them of the situation. Since we were already inside the ZZZZZ intersection on the ZZZZZ1 arrival into ZZZ1; it made more sense to continue to ZZZ1 than look for alternate airports. Dispatch agreed to continue. I transferred the flight controls back to the FO so he would regain PF duties and I took over the radio and PM duties. I looked once again at the overhead Pressurization panel and saw that the CABIN ALTITUDE AUTO RATE CONTROL knob was in the Min position and not in the INDEX as normal per preflight procedure. I asked the FO if he turned that at some point while running the QRC or accidentally bumped it; his reply was that he did not touch it. I put the control back to the INDEX mark and the CABIN Altitude Warning light went out a few minutes later. The FO set up and briefed the arrival and approach into ZZZ1 for Runway XXR. ATC vectored us around and we flew the ILSXXR without issue and taxied to the gate. The pressurization functioned normally for the remainder of the flight. Normal procedures were performed and flight was debriefed.