More food stamps?

I had about 10 dollars left out of the little I get from food stamps so I after grocery shopping I swiped the food stamps first and I was going to pay the rest in cash. Well the whole purchase (only 20$) went thru and I was preoccupied that I just walked out and didn't really notice until I got into the car and looked at the receipt what had happened. I called my card and it was the full amount again minus 10$. I'm so confused but then I checked the website and it says food balances amount may change Oct 1st because federal cost of living changes. Any one else have this happen?