Expected result of using these two flags at once

[curlyboi]

I thought that this would compute the total number of hashes in that range (1 - 10) and attempt to crack using the first 400 generated guesses and then stop.

First, dont use -s and -l with increment mode.
Second, the -s and -l are not normal password units. They are what I call KU (keyspace units). Run that command with --keyspace to know the total number of keyspace.