How to close a hole created by an extrude -> boolean difference


I’m numbering 100 models and I am doing that through the string and extrude nodes. It works, but I need to copy paste them to all 100 models, change the string and then export each model.

I am having trouble however, with a hole that is made due to the extrusion - boolean difference. When I print it, it’s fine, but I would like to have it fixed so my model doesn’t show any errors.