Double subscript notation
Double-subscript notation is notation used in Electronics to indicate the direction of current or voltage. This is a convention to standardize the directions of double-subscript labels. The convention works like this:
VCB means the "V" from C to B. In this case, V would probably stand for voltage, C would probably denote the collector end of a transistor, and B would denote the base end of the same transistor. This is the same as saying "the voltage drop from C to B". Although this assumes what the letters are, presumably this notation can be used in other contexts.
ICE means the "I" from C to E. In this case, I would probably stand for current, C would again probably denote the collector end of a transistor, and B would denote the base end of the transistor. This is the same as saying "the current in the direction going from C to E". Although this assumes what the letters mean, presumably this notation can be used in other contexts.