Topping off

When you finish your extract boil how do you guys top off?
I am doing my first batch this weekend and trying to get all my last questions answered.
My recipe says to boil 2 to 2.5 gallons of water for the split boil and then top the rest off in the carboy. I am not sure what type of evaporation I am going to get after adding all the extract and what not since I am new to this.
After I finish the wort and add it to the 6 gallon carboy should I just be topping off to
the 5 gallon mark or leave the evaporation into it and just add the rest of the water...2.5 or 3 gallons the difference of what I started with?

Mark a 5 gallon mark on the carboy and throw in about 2 gallons of cold water, pour the cooled wort on it and fill the rest of the way to the mark with water. Be splashy!

I did a 3 gallong boil yesterday and rinsed my grain with a pint of water, so 3g1pt , boil for an hour and I still had to ad 2.5 gallons. So a half gallon+pint lost to evaporation. Fermenting nicely. Don't over think it. YMMV, BTW don't drink while doing your first one.

Fill it to the 5 gallon mark. Why make less beer?

Actually, I try to make 5.5 gallon batches, 'cause I know I'll lose a half-gallon or so to the trub. If you do that, you'll probably need to hook up a blow-off tube to the carboy, but that's easy enough.

Thanks guys I just didnt know if topping off to the 5 gallon mark and the evaporation is all included in the recipe, did not want to water anything down.
I am using a kit for the first time so I dont want to go as much as 5.5 gallons to make sure I get 5 gallons of beer, I would have to get more ingredients to do that and figure out how much more to add to the kti