Define how many N-matches are accepted:
'Accepted N-matches' defines the amount of N-matches that are accepted wothout causing a mismatch.
'N-match limit' defines an upper limit for N-matches. Whenever that limit is reached inside one probe, all N-matches count as mismatches.
Define max. results:
The number of hits is limited to 1 million by default.
This is just there to protect you from waiting several hours for match results, just because your settings were too lax.
Changing it to 0 disables the limitation.