I have a live app with tens of users that have created more than 11,000 of a Data Type
An alert saying List at maximum length (1000) appears when a user tries to create that Data Type.
But there is basically 1,000 entry limit on Lists. There’s no row limit on an actual Data Type. So it sounds like when your user is creating a record of said Data Type, it’s also being added to a List. Depending on your use case, there are likely better ways to handle this (usually in the form of an additional Data Type that links them).