You have many multiple editor windows open and in each also use many tabs.
TOAD happens to crash for some reason.
After restart you are presented with option to restore them, which you want to do.
With each entry being restored to separate editor window you'll have their number = previous editor windows * previous editor tabs.
But more likely TOAD will freeze/crash on restoring them, as each editor windows uses approximately 410 GDI handles, while new editor tab takes only 28 handles.
On Windows 10 the limit of GDI handles is 10k, and can't be easily changed as in previous versions (AFAIK).
Restore the editor to tabs as they were, or allow to change it while defaulting to previous session setup.