If that 10k is representative, that should give a very small uncertainty interval, less than 1%. You can get 95% confidence interval with only a few hundred samples depending on the standard deviation, so 10k is actually massive. It's pretty standard statistics, here's more info on how it's calculated.

https://ecampusontario.pressbooks.pub/introstats/chapter/7-5-calculating-the-sample-size-for-a-confidence-interval/