Field help (RATMUL) 

Use this field to define the factor by which a project, or employee labor rate is to be multiplied. For example, type "1" if this time category equates to standard working time; type "2" if this time category equates to a rate to be paid at double standard working time.

A rate multiplier of "0" (zero) is permitted. If this time category equates to a zero rate, this will result in the amount of time (in the defined time unit) spent working on a project being recorded, but the value of that labor time will be zero.​