The base of this table is set well inside the edge of the top, and the reason is chairs.
A dining table is judged, in daily use, by whether every seat is comfortable - and the seats that are not comfortable are always the ones where someone's knee finds a leg. On a table with legs at the corners, the two people at each end are fine and the ones sitting at the corners are not.
A shaped base solves it, but only if it is set out from the seating rather than from the table. So the working drawing for a set like this starts with the chairs: their positions are marked around the oval at the spacing you want, then the base is drawn inside all of them, with the end sections pulled far enough in that no chair pushed under the top meets anything.
The top overhang is set from the same drawing - generous enough for a chair to tuck fully under, without becoming so wide that the top looks to be floating off its base.
Change the chair count and that drawing changes, which is why we ask for it before anything is cut.