__COMMAND_NAME__ is a column in the User Calc function [IMUC]. The tab in IMUC for COMMANDS shows a table with the first column listing a 'Command Type' followed by a 'Command' and then the 'Command Name' followed by a 'Description'.
\\Example:\\
Calculation     XPPT    __Exit the Pay Point Set__   UC in progress to immediately proceed to  99999\\
In this example 'Exit the Pay Point Set' is the Command Type.