Extra data appended to the Y values when issuing `M92` & `M500`
*75 is the checksum value, (a method for verifying the integrity of the transmitted information).

RepRap wiki gcode : checksum

There is probably an option to not use/disable checksum generation in repetier/slicers, however this may only be advantageous for use with code run from the sdcard as it is extra processing (and probably less relevant when not being transmitted over serial connection. )