hiwin rail hole placement question

hello all
ive been out for a while due to family issues work commitments etc sold up a while back and soon regretted it...the boredom on weekends has forced me to build another fixed gantry router..looking at 3030ish
I'm about to get into the drawing stage,ive found the hiwin rail I'm after which is HGR15 L600mm .
working in sheet metal with several big laser cutting machines at work I'm opting to have the gantry and most everything else laser cut 4mm plate, castleations all round,plenty of gussets and a bit of welding,as much a flat pack affair as I can get away with,,,anyways I need to get some dimensions drawn up for the laser lad,im looking at the supplied drawing on the sellers link to the rail and it says for the 15mm rail dimension E means the first hole(centre) is 20mm from the beginning of the rail and the P dimension means each hole centre is 60mm apart..all good but then it shows a diagram of the end of the rail and the dimension E=20mm..,but my rail being 600mm will mean the last hole will finish 40mm away from the end.
am I safe to assume that's how it will come 20mm one end 40mm the other or will it come evened out so E is 30mm each end? sorry for what might seem a daft post I'm not up on buying profile rail.

Good to hear you're back :)

Your machine work area is quite small, so it may be OK, but I'd seriously consider using 20mm rail compared to 15mm. When you see both, it looks quite a lot bigger which in general makes the design easier. I've got some spare hiwin HGH15, but haven't used it partly due to the size.

As to the question of the holes, I would ask the seller as they can probably cut it to whichever you prefer. The spare 760mm pieces I have have the holes centered, so 20mm from both ends.

thanks jon ye I messaged the seller but no reply yet,i guess I can carry on and ad the rail hole placement later on in the drawings.
il see what deal I can get on 20mm all round