How much could you express?

My baby is two weeks old today and exclusively breast fed. I’ve just pumped for the first time on one breast as it felt slightly engorged (not painfully so just been about 3 hours since she fed off that one). My baby typically feeds for ten minutes or less off one breast for a feed and can go anywhere from 20 minutes to 4 hours between these length feeds.

I just pumped on one breast for about 10 minutes and got 4oz. I feel I could pump more from it but stopped as I’m not planning on offering a bottle and am just keeping the milk as a just in case. Is this enough? It doesn’t seem like a lot when I look at it in the bottle and I’m concerned her irregular feeding pattern is due to a lack of milk 😓😓😓