Opening explorer move count wrong

I was looking at the opening explorer in a Daily game :-

You can see here I played 1. e4 c5 2 c3 Nf6   

At this point the opening explorer only shows 2 games continuing 3.d4  , but when I made the move 3.d4 the opening explorer then looks like this:-

Where did all the extra games come from? Why were they not shown one step before?

The explorer does not show the matches played but the number of positions!

From the position after 1. e4 c5 2 c3 Nf6    only 2 played d4

BUT

the position after playing d4 was also reached from many other starting moves, like after this move order

1. d4 Nf6 2. c3 c5 3. e4

Ah, I see. So this position has been reached lots of times, but not necessarily by this particular move order?  This is a transposition into a more popular opening?

yes

Therefore this has to be considered when reading the explorer. Its not that simple as it looks like and easily bring you into trouble when only checking a position and the explorer results.