Tissue expanders and reconstruction

Hi Wendy I saw your post and have a quick question if you or anyone can answer. I had 280 removed from my breasts and 300ml expanders put in, I was keen to go a cup size up but got the impression that you could only fill the expanders to whatever size was put in, I.e I couldn't expand above 300mls as that's the side of the expanders- do you know if this is correct or whether you can keep expanding until you're happy? I'm super anxious about it so any information is appreciated! Thanks, Erica