Correct me if I am wrong, but this scenario would mean we get #33, but we also get #33 if we both stay in the Top 4, but get the higher pick.
Five Scenarios:
Both Drop Out of Top 4 = Spurs Get 32
Spurs Drop Out of Top 4, Rockets Stay In = Spurs Get 32
Spurs Stay In Top 4, Rockets Drop Out = Spurs Get 33
Both Teams Stay In Top 4, Rockets Pick Higher = Spurs Get 32
Both Teams Stay in Top 4, Spurs Pick Higher = Spurs Get 33
We could of course calculate out all these probabilities, but I'm not going to take the time