Be sure to ASK them how much is in your band. If you've been going to the same doctor, they should know. If they don't, then they need to. They can take it all out and re-inject it so they'll know for sure. It's YOUR body, it's YOUR money.... don't be afraid to ask them!
By the way, I have a 10cc band, and I had it filled about 10 times, finally getting 9.3 cc in my band. That was a little bit too much, so I went in and wanted .5cc taken out... Well, she took out the whole thing and then started putting it back in, starting me at 7cc again. No restriction at 7cc. Went back again and up to 8cc. No restriction at 8cc. Went back again and up to 8.3cc. Very, very slight restriction. So I'm headed back again tomorrow and going to ask her to put me up to 8.7 to 9cc. I feel like I KNOW my level after 3 years, and I KNOW what is best for me.
Don't be afraid to stick up for yourself!