I'm trying to updated a field so that it has specific constraints on it and every time I go to change it, it gives me an error message. The field is currently a text field, and I want to change it to a number field with a range on 1 up to 100 000. 

I've done a search on all documents with this field and they are all numbers and fit within this range, but I keep getting this error: 

How do I fix this field?