Cart loadout question Pickering xv-15/750E on Empire 598 turntable

I just got a vintage Empire 598 turntable with a Pickering XV-15/750E cart. I run into a McIntosh c2700 tube pre that will only let me set the loading to 250pf or 300pf but not the 275pf in the cart specs. Not sure how to set this? I can also go even higher 350/400 and up. Any advice would be greatly appreciated.