Filling clutch master cylinder

Queston on initial filling of clutch master cylinder with fluid. There is a rubber cup under the cap that extends well into the reservoir. Should I leave the cup exteded are push it in toward the cap. If I leave it extended it trys to push the fluid out. If I try to push it in it does not want to stay collapsed.

it is supposed to be folded up to the cap. it is designed to be a seal that will expand into the cavity as fluid gets lower to keep moisture absorption from free air to a minimum.

Exactly what I was thinking. It does not want to fold up. Let me try it again tomorrow. Ready to get it installed. Thanks

Like a turtle neck or a foreskin, it folds back on itself.

ETA it doesn't really need 'reserve'. As the clutch wears the fingers push the throwout back.
The reservoir only has to hold the slack.

dont make it weird

Really?
That's exactly how it works...
Every male ever born is weird?

The whole planet can relate (except for those freakish puritanical places where art history professors can't critique Michaelangelo's David)

Edit: Gary can nuke this if he likes, you should ban me at the same time!  😄