6. $A, B$ two people are playing a table tennis match, with the rule that the first to win 3 games more than the opponent wins. After 13 games, $A$ finally wins with a record of 8 wins and 5 losses. Then the number of all different possible outcomes of these 13 games is $\qquad$
6. 243.

As shown in Figure 3, use the grid point $(m, n)$ to represent the moment when $m+n$ games have been played (with $A$ winning $m$ games and $B$ winning $n$ games). The problem then transforms into finding the number of grid paths from $(0,0)$ to $(8,5)$, where the points $(x, y)$ passed through satisfy $|x-y|<3$. Clearly, the grid paths lie within the polygon formed by the vertices $(0,0)$, $(2,0)$, $(6,4)$, $(8,5)$, $(3,5)$, and $(0,2)$ (including the boundaries). Using the labeling method, the number of grid paths that meet the conditions is 243.