During the credits of Pokénchi 104, it was announced that this episode was the 1000th episode of the main series.
PocketMonsters.net's numbers this episode 993 as we do not include the 10 specials as part of the main series but we do list the 3 unaired episodes. These two adjustments give the 7 episode difference between our numbering and this announced official numbering. When these 10 specials originally aired, they were announced as special episodes and as such we treat them as OVA/Specials.
Also note that the official production numbering differs from this announced official main series numbering. Production numbering is listed on the covers of anime scripts such as the unaired BW 24 which now isn't included in the official main series anime numbering.