Agreed...I do only 1 gallon batches and you really need to dial in your numbers and this won't be an issue. I start my boil with 1.87 gallons and end up with 1.15 exactly (at least for my IPA). After filtering and cooling, I get slightly over 1 gallon in my fermenters.
If you are using a 1 gallon carboy there is no way you are ever going to get 1 gallon for bottling, trub loss, blow off, and racking will leave you with less. At best I get 7 16 oz bottles, at worst, 5 with a half-pint sample.
Two things you can do...break your batch into 2 1-gallon jugs and brew 1.25 or so gallons, you'll get 1 gallon in the end. Or get a larger fermenter for it and do the same. I simply due back to back brews so I only have to use one yeast packet and I get a 12 pack of 16 oz almost every time, sometimes I get 14!