Sure enough the new bag's volume was 2 ½ quarts not 2 quarts like the old one.
I had the same thing happen to me when I was fourteen. The following is how it happened.
My girlfriend had issues with period cramps and one afternoon while doing homework at my house, she asked my sister to give her a couple of enemas. My sister agreed and the two girls disappeared to the bathroom giving her the enemas she’d requested. During the enemas that afternoon, my sister told her about our after-school activities and how we got started not long after our RN grandmother taught us personal hygiene during a summer visit. That fall after school started, my sister and I got home from school one afternoon both constipated and needing a couple of enemas. When I told her, I needed the bathroom and why. She informed me, she had the same problem and suggested we give each other a couple of enemas. I liked the idea an agreed, besides, I missed someone giving me an enema and I suspect my sister did too. So, we both got undressed and went to the bathroom. We gave each other a couple of enemas that afternoon, starting our weekly after-school enema sessions. My sister liked using the curved douche nozzle for enemas because it stayed in place, felt good, and went in deep. So naturally, without thinking twice about it, she used the curved douche nozzle on my girlfriend that afternoon. Following our normal routine when giving each other enemas, she started moving the nozzle around as the warm water flowed in. My girlfriend loved it an asked my sister a lot of questions about it. Telling her, my brothers do it to me, just like I did you when we give each other enemas, and vice versa. Then said, "Ask my brother (meaning me) next time you need a couple of enemas, you won’t be sorry, he’s good.” A month or two later, she did just that.
We swapped enemas afterwards on a monthly basis every other day during her period at my house in the beginning. A few months later when we used her house for the first time, I had trouble taking a two-quart enema. My girlfriend was first that afternoon and took both her enemas without issue. When it was my turn, I had trouble taking the two-quart soapy enema. That was unusual, because I normally didn’t have any trouble taking a two-quart enema. Just two days before at home, I’d taken both a soapy and rinse enema without a problem, as did my girlfriend. I did manage to take the full bag, but it sure wasn’t comfortable. The same thing happened during my rinse enema, and it really had both of us puzzled. Out of curiosity, my girlfriend went to their linen closet and got the box the bag came in. When we looked at the box, we both got a big surprise, her mom’s bag was 2½ quarts not 2 quarts like the bag at home. Two days later, we were back at my house, both taking a soapy and rinse enema without trouble. When we finished, we checked the box in our linen closet and sure enough, it was a two-quart bag. Afterwards, we started splitting our monthly sessions between our two houses, and it only took me a time or two before I was taking 2½ quart enemas. Switching between houses also allowed me to be around her younger sister (by a year) and I quickly realized she was just as anal erotic as my girlfriend. Learning from her, the two girls had been giving each other enemas for some time. Like my siblings and I, the two sisters were giving each other enemas on a weekly basis. That’s when I realized why my girlfriend didn’t have any trouble taking a 2½ quart enema, unlike me, she’d been doing it for some time.