A number followed by も expresses the speaker's feeling that the number is large.
わたしは きのう 八時間も べんきょうしました。
I studied as many as eight hours yesterday.
すずきさんの うちには 子どもが 十人も います。
The Suzuki's household has as many as ten children.
Unlike しか which can be used with both numbers and general "quantity words," も is only preceded by "number words."
I ate a lot.
I drank all of it.