What's this speed thing?
When SecuPress runs a scanner, it literally sends about 30/35 ajax requests at the same time. Don't worry this is not bad, but some servers, but configurations doesn't allow or like that and then, some scan results can never be done.
This can lead to false results, or you always encounter a "New scans !" green box (means, previous scanners didn't end well), or some other unexpected behavior.
Do prevent that, you can set a speed for this scanner, max speed is the usual one (mean, no delay), normal will add 0.25 second between each scan and low will add 1 second.
If you need to set a custom value, you can use the filter hook 'secupress.scanner.scan-speed', returning an integer value in milliseconds (1000 = 1 sec).