Where are the 3 extras? If in Ancestry, it could be that Ancestry needs to add a person to certain situation: I had it somewhere for the grand children of my uncle I think, who had to be adopted by another member of the family after the death of their mother in a fire -> they were duplicated since they could not have 4 parents.
Some partners like myheritage also need to add 'empty people' to all unknown parents (if I export RM to Gedcom, import it in Myheritage and export gedcom from Myheritage to RM back, I get a few hundreds extra people, without names). I guess Ancestry might face similar needs in some cases.
If 3 extras in RM, maybe you have 3 people in a separate tree (tools count Trees) -> I am not sure Ancestry would include them if he can not find a relationship with an existing person.
I personally export a gedcom from RM and import it to Ancestry, I find the process much quicker than validating each changes