Address line A11 is not connected to a 2k rom, so the rom is mirrored twice in the 4k address space. Addresses '$F7FC' and '$FFFC' both point to location '$7FC' in the 2k rom.
These aren't the only mirrors you can use.
In 4k rom, address lines A15,A14,A13 are ignored (those pins aren't present at all on the 6507), A12 must be '1' to select the rom and A0 to A11 are used to address the rom. This results in the rom being mirrored 8 times in the entire 16bit address space:
In a 2k rom, in addition to that, A11 is also not connected and only A0 to A10 are used to address the rom, so in this case there are 16 mirrors:
You can use any of these mirrors in your program, as they all point to the same phisical memory.