Categories usually define the price for general admission tickets for home areas based on demand with category A tickets the most expensive for supporters.
In past seasons the Spurs v West Ham game has always been priced as category A so the news is somewhat of a surprise.
The re-categorisation makes no difference to West Ham away fans with the away ticket price still fixed at £30 for all games no matter what the category is but Hammers fans will nevertheless feel like it is a snub to the Irons.
Last season West Ham became the first team to beat Spurs at their new stadium when Michail Antonio scored on the 67th minute to make it 1-0 at full time on 27th April.
The attendance for that game was 60,043. The capacity of the new stadium is supposed to be 62,062 but the record attendance set so far is 60,243 vs. Ajax (30 April 2019, UEFA Champions League)