Before version 5.3.5, in the number field within the form, there was no decimal place validation which could have caused an issue when linking to an iSheet that does not require validation. Number fields now have the same decimal option that collaborate iSheet number fields have: 0,1,2,3,4,5.
2. For existing forms that have a sync to iSheet action; if the field is already synced with the iSheet, the field will already be synced. Therefore, the old field will need to be removed, populate the new number field with the decimal validation and sync again, as this will not change the decimal number property in the iSheet