on a manifold gage set for refrigeration what do the rows of numbers stand for or what do they mean?

Answer 1

It is a pressure temperature chart. The outside black numbers indicate pressure in PSI. The inner smaller red numbers indicate the type of refrigerant, such as R-22. Say on a R-22 system, the evaporator should have a 40 degree coil temperature. That would equate out to 68.5 PSI on the black, and if you read down to R-22 you will see it is 40 degrees Fahrenheit. That is for the blue gage (low pressure). These gages tell you if your system is properly charged. Chow

Answer 2

red high side pressure blue low side pressure