In the admin interface, input fields having to do with a specific number (e.g. maximum number of fines) should be required to be filled out with numbers.  (This is already the case for some of them, but not all.)  In cases in which the number is intended to be within a particular range of values–e.g. the "minimum quality" field in the library form, in which the label specifies that the value should be between 0 and 1–the interface should validate that the input is in fact within that range.