If you were sentenced to 12 months probation, and you only have 4 months left, the judge cannot revoke more than the balance you have left on probation. Nor can the judge add more money. He can revoke the balance of the probation but that would absolve you of the remaining financial obligations you may have. Hope that answers your question.
Also, Attorney Yeargan is right in every respect to this question - how to succeed on probation.