Vulnerability scanning - how often? force scan?

Vulnerability scanning - how often? force scan?

We have the Endpoint Security addon for Desktop Central and I've been busy fixing out of date software.  (starting with the Critical over 90 days).   I feel like I fix 90 bugs, but the list only goes down by 40.. or something like that.   then the next day list goes down more.   
When does the Vulnerability list get updated?  can I force it to update?

thx

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