A Line Mechanic reports he incorrectly applied an MEL Maintenance Procedure to a deferral of the Standby Pressure Controller Transfer Lockout Light on an MD-80. Aircraft was unable to pressurize at takeoff requiring an air turnback. Mechanic noted the MEL Maintenance Procedure page appeared to apply to MEL 21-23A and not just MEL 21-23B.

Narrative

I received a gate call for an aircraft for 'Transfer Lockout Light On' for the Standby Pressure Controller. I called Maintenance Control and received an MEL 21-23A and corresponding authorization. While reading the MEL; I saw a Maintenance Procedure on the same page (which I later found out was for MEL 21-23B) which I thought applied to MEL 21-23A because the MEL and the Maintenance Procedures is attached to one block on the [MEL] page. By accomplishing the MEL (pulling the controller # 1 and # 2; H2 and J2); this caused the aircraft to become unable to pressurize at takeoff and caused an air interrupt to ZZZ. I was notified by phone that the incident happened and decided to accomplish this report. If there is a Maintenance Procedure for an MEL; it should state clearly which MEL it's for. Also; if a MEL does not have a Maintenance Procedure it should not be on the same page as an MEL that does have an Maintenance Procedure. The first suggestion to me is best because had the Maintenance Procedure stated somewhere that it was for a specific MEL; I would not have been confused. I was confused while accomplishing the MEL because I knew I was pulling the [Circuit Breaker] collar for the Controllers; but I thought I should follow the Maintenance Procedure anyway.I had placed the Alternate Pressure Controller on placard using MEL 21-23A. The MEL page has a Maintenance Procedure on the bottom for MEL 21-23B...but it is confusing because it looks like the Maintenance Procedure applies to both MEL 21-23A and 21-23B; it is very confusing as to how it's laid out.