This page shows the cards that have shot up in price from under 25c to over $1 in the last year - they've broken out of the "bulk" price range, and are now sellable
If the VAS is higher (Vendor Agreement Score - the number of vendors we track where the card has broken out), then more vendors agree, you definitely want to pick these out of your bulk storage.
If the VAS is lower, this might indicate a potential spec target, on the way up
PS - thanks to the Brainstorm Brewery podcast - "Breaking Bulk" is named after one of their regular show features. Go give it a listen if you want great MTG Finance Content!