That's probably referring to Terminal 2A, the main building for T2, as opposed to the B satellite. Gates are not guaranteed at LHR (unlike the US, the airlines don't 'own' them) so in theory this could change - although it's probably unlikely given B gates are mostly used by UA, AC & SQ because their lounges are based there.

in terms of your planning, it makes no practical difference to you even if something unusual happens - it's a 10 minute walk between the two, but you're processed at T2A.