Why Is My Photo Library Bigger After Fixing It?
A corrected library sits alongside your export, so you briefly have two. Here is how to manage the space.
Because for a while you have two copies: your original export, and the corrected library written next to it.
That is deliberate. Writing into a new folder means your download is never at risk, and a run you dislike costs you nothing but time. The trade is disk space, and on a large export that is real. Plan for roughly double while you work, then reclaim it.
Once you have checked the new library and backed it up, delete the export and the zips. You are back to one copy, and it is the good one.
The app checks you have enough free space before it starts and says so rather than filling your disk halfway through. If space is tight, work through one album at a time. The first 500 photos are free, which is a useful way to measure how much room a full run will actually need.