What is an 8.75 pinion offset?

Stupid question time. I've read somewhere that the pinion offset in an 8.75" rearend is 1 3/16". Does this mean the pinion is 1 3/16" from the center of the housing? I'm getting ready to order custom axles, and they wanted to know the length from the center of the pinion to the outside of the drum. Why is this measurement important. I want to keep the axles equal length. I know my drum to drum measurement is 51 1/8".