Imagine it works like this(I'm going to make up some numbers but they're reasonably close): Of the entire DoD budget, 75% is non-discretionary spending(health care, retirement, etc) so you actually operate with 25%. Well, let's say we've spent 12.5% already since we assumed Congress would sort this thing out, so we've got 12.5% remaining. So once a 10% cut is taken in the remaining 6 months left, 2.5% is remaining for the next 6 months and somethings are contractually obligated (JSF) so operations and maintenance takes the hit.