Originally posted by Mark Adkins
In the Master Games section of the database, after 1. e4 c5 2. c3 e6 3. d4 d5 the games explorer shows 50 games featuring 4.e5, and of these White is shown winning 24%, Black winning 34%, and 42% drawn. However, after actually clicking on 4.e5 there are now shown not 50, but 673 games; and it is clear that Black is ...[text shortened]... ? Now it suddenly reminds me of chessgames.com's Opening Explorer, which was always confusing.
As I understand it the positions are kept in the database by FEN, but you access those positions move by move.
The transpositions of the opening moves may lead to these variations in numbers - I'd guess that the particular sequence you outline arrives at a position that is more commonly arrived at by another sequence of moves.
There are glitches in the current incarnation of explorer as well, I know that certain sequences get mashed because of errors in the FEN - case switching for example, leading to some opening lines that cannot be followed through.