Question for Alan D. APU offsets

Alan,
Need some Offsets for dummies help here! :confused: :D

PMSystems, in particular, the APU control offset. Here are the ones from the docs from PMsys,

APUStarton,0

APUStartOn,1, .5 // what is this .5 ??

The offsets are APUMasterOn 5601.0 can't get this one to do anything
APUStartOn 560F 1 This turns the APU on/off but no start position

APUMode 560E 1 I think this is used to monitor the status of the apu??

As you know, in our 737's we have a 3 position switch we need to wire to start the APU upon release from the start position.

Thanks,
Rob