Yup.
Quick math and being paranoid about redundancy:
A typical period lasts 3-5 days, with 7 being the high end. Round to 10.
Heavy flow might require a change every 4 hours, or 6 a day. 12 a day is in the realm of reality, albeit medically concerning.
Bring extra in case return has to be delayed for whatever reason.
They’re extremely light and small, so a conservative weight allowance holds a lot of them. About 1g each, or 100 per 4oz.

So some quick math and padding your numbers to account for the unknown gets you 100, which considering they then asked isn’t an unreasonable way to start.