And this FX vs F2A craziness wouldn't have happened if only all Green card (LPR) candidates included their spouses (and children) in their original applications as derivative beneficiaries.
So I believe this is how the system plays out. At the beginning of each fiscal year (October), Spouse applications start pouring in. Officials see that the Exempt category of FX is fresh, open with ~65,950 spots available (75% of 77% of 114,000). They start filling them in. By let's say around May of following year all 65,950 spots get filled up. Then they start the F2A category, with ~21,983 spots available, BUT with country limitations. No one country can get more than 7% of this 21,983 spots. So it's possible that the first 14 countries with the most Green card hungry applicants can theoretically fill out these spots (7% x 14 ~ 100%). If you are on the 15th country, you are out of luck,- unless there are some leftovers from other categories.