ok, then next time I'll boil less then 3gal. I guess I'll try 2.5gal. since that should get me to my 5gal. magic number.
I think I misunderstood your question and owe you a huge apology for my confusing and not very good advice. Did you measure and read that you had filled the fermentor to 5.5? If so, ignore **EVERYTHING** I've told you.
Heck! Ignore everything I've told you anyway. I'm just a newbie who has only brewed 3 batches and *none* of them are out of the bottling stage yet. (Oh, except for the *very* first Mr. Beer batch which doesn't count.) I don't know what I'm talking about! I'm just some stranger on the Internet.
The way I read your first post, I thought you *hadn't* read the water level but were assuming 3 + 2 and the extract had to equal 5.5 so it had to be over.
In general you want to boil as much of your full ammount as you possibly can. If you can only boil 2.5 gallons. That's fine. If you can boil the full 5 gallons that's great! If you boil 4 or 3 gallons that's fine. Then you simply top off to the full 5 (if you have to). That's it! Don't complicate further.
Pouring wort into a fermenter that already has water in it? That's fine. No big deal. If the water has been chilled or frozen that'll even help cool your wort. Of course, if you put water in before you'll have to be sure that you don't put in more than you should. But that's easy, if you're boiling 3 gallons don't put in more than 2. If you're boiling 4 don't put in more than 1.
And if you screw up the math and the final batch is 5.5 gallons instead of 5 gallons... well, just shrug and scratch your head and wonder how it happened[*] but don't fret. It's not a big deal.
I'm sorry if I've given you confusing advice. It wasn't my intent. But maybe that should be a learning experience too. Don't try yourself in knots and second-guess yourself over some advice some bozo on the internet tells you. The guy just might be an idiot.
--woozy
[*] I don't think it could be because of the volume of the extract; I kind of assumed that extract was completely soluable in water and wouldn't increase the volume but what do I know... I'm guessing you simply mismeasured and put 3 gallons in instead of 2. Or boiled 4 instead of 3. I'm actually kind of impressed that you didn't have evaporation because I seem to always boil off *huge* amounts.