Regarding hs_multi_compile and hs_scan functionality

I am having doubt regarding multiple regex scan.
Let say I have 30 different regex patterns to scan on a single buffer and I compile all of them using hs_multi_compile in single database, then used that database in hs_scan, so will hyperscan scan buffer separately for each pattern , or will it scan complete buffer single time for all pattern. (ps. - Point is how many times buffer will be scanned.)

Also if it scan's separately , then how it will be more effective or efficient than compiling all pattern's separately using hs_compile and then calling hs_scan separately for each pattern.