Please can you offer a definition of the terms 'Stock Tank' (as in Stock Tank Conditions) and 'shrinkage'. Is Stock tank condition the same as standard condition (1 atm, 60°F)?
Stock tank conditions are standard conditions, that is 15 deg C and 101.3 kPaa (or other units as required).
Shrinkage measures the difference in volume flow from reservoir conditions to stock tank conditions, alloqing for the light ends to flash off from the crude.