There is no formula for recarbonating a keg. You can take your chances and rolling the keg will help but there is simply no way to know how much or little gas you are imparting into the beer. Once you have consumed this keg, target 38 degrees liquid and 14 PSIG on the next one. Research other posts on this site as to correct set up. No idea what your are referring to as to the knob on the beer pump[?]
Scott Zuhse, Instructor
Micro Matic Dispense Institute