Thanks for posting your question in the Microsoft Q&A forum.
you can expand the database from 100GB to 140GB if you still have around 44GB of free space in your elastic pool. This should not be an issue.
The maximum size of a database inside an elastic pool cannot exceed the maximum size set for the elastic pool itself. If the elastic pool has a maximum size of 200GB, no single database inside the pool can exceed this limit.
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