Looking at the new options introduced in JBIDE-15287, I don't quite like to look of it.
Let me know if you disagree, but using "(default)" in a field that's supposed to take numbers is not very nice.

Instead, I propose adding a checkbox in front of the options:

Excuse the ugly picture, but the idea is that if the checkbox is not checked, the field is greyed out (and empty). If it is checked, a value is expected. WDYT?