You are partially correct. Yes, an Inf Bn has 8 Atgm/RR but they are under a Sp Pl in the Rifle Coy, not as a separate SP Coy.
Also ANNX-17 shows that 8 are available from the "Divisional Resources", which indicates its from one of the 3 AGTM pl of the ATGM Coy of the Div SP Bn. Also the...