Alibaba’s revenue is (primarily) only the fees and commission they charge their sellers. They did $30B of gross sales on that day but probably only collected $1-3B in reportable revenue. Amazon does the same thing for it’s third-party sellers; only the fees and commission make it to Amazon’s top line revenue number for seller sales.

It looks like the one-day number is gross (ie, no costs subtracted), the other is net profit.

They allow you to order in advance for discounts, and book all the sales on one day as a PR exercise.