Is it grammatically correct to substitute two people for just two in the following sentence?
I have seen three people in the street: two (people) beneath an oak tree and one at the corner.
It is English to do so. We know, whom you mean by using two, too.
I still need more definite answer, please help.
This isn't related to your question, but why use the present perfect? Why not simply say "I saw..."?
There is no definite aswear! Just translate it into your mother tongue!