Number + もEmphasis, As ~ as, Not even

The adverbial particle も is often used for labeling (A) as part of a category, when it would not usually be considered part of that group. In this way, it emphasizes that (A)'s inclusion is something that is surprising/unexpected in some way.

When も is used after a specific number + counter, it shows that the number itself is surprising. This can be when the actual number is lower, or higher than what was expected. Due to this, も can translate as 'as much as (A)', or 'not even (A)', and other similar phrases in this expression.

At first glance, this may seem different than も's translation as 'too' or 'also', but in those cases, も is also just pointing out the something unexpected is part or whatever group was initially highlighted.

The above sentence just shows that the (B) speaker is unexpectedly putting themselves in the group that the (A) speaker initially only considered themselves to be a part of.