How many oz for 5 week old?

Courtney
I've started pumping this week in the hopes to have enough for just one night out with my husband! I haven't been able to get much per pumping session, but I do have about 5oz saved. My girl will be 6 weeks on Tuesday, any suggestions on how much I should leave for her for one feeding? She's never taken a bottle before, so I'd like to try giving her just a little bit to make sure she'll take it before leaving her, but I just want to make sure I don't leave too little!