Preconditions: created content type with image field type
Steps:
1. Go to Edit mode of content type from preconditions
2. Put a value in maximum file size (for example 100)
3. Click OK
4. Go to the edit mode once again - the field with max value is empty

Update: you cannot put a number lower than 1 000 000 B (1MB). So if it will be too much complicated to fix that, we can add some information for a user that there is a minimal value for this field.