2 Colour Ryobi Numbering and perfing HELP!!!

When im doing perfing i seem to always be getting a squint perf towards the tail off the sheet, when printing on sra4 size it is the worst and wondered what i can do to fix it ?


Also i am new to the machine and numbering unit etc and was wondering if there is a quick way to set up the numbers and perf instead of guess work??? just wondered with the graph on undercylinder etc.

Thanx