If a team below Toronto (thus below the Spurs as well) jumps into top 4 the highest the Spurs can pick is 6, that's because there would still be 4 teams with a worse record than the Spurs fighting for only 3 spots, so whomever doesn't make the top 4 will have no. 5 before the Spurs.
That said, yes, you're basically correct in that for the Spurs to get a top 4 pick AND the Toronto pick to convey then not only Spurs have to jump but also one (or more) teams besides Toronto (but not them). The odds a team below Toronto jumps (but not Toronto) are (roughly) 54%, if you add the constraint that the Spurs also jump to top 4 then you get to that 22.74% I said. If you want top 3 and not top 4 then that leaves you at 17.14% (add up the cells that are in rows 1-3 and columns 7-10)
Basically whatever scenario you want to find the odds to, simply find the cells in the table that meet that criteria and add them up. In the case you mention I already did it because it was precisely what I was interested in finding out and that's why I had already posted the number.