What does "50 (or 250, 500, ...) artworks" mean?

The 50/250/... is the maximum number of artworks you can have in your account, but you can delete/replace artworks anytime.

Our tiered payment plans allow from 10 artworks on the free STARTER plan up to a maximum of 500 on the PROFESSIONAL plan to be uploaded. Once uploaded, your works can then be used to create 3D exhibitions or be published directly from your ART.DEPOT.