Why can the user enter some non-number characters in a number field? Why isn´t this blocked just in time? It should be possible
Only when he save the form/document he will get a "cannot convert text to number" error message and this produces some user-frustrations.
What I would like to see is a just-in-time check if the user enter only number or a better way... let him enter only numbers and when he press a character block the input.