ASM maximum number of entries in manual learning?

I noticed on my ASMs that occasionally the entries for say an attack signature show 0 Recent Incidents or if you go into a HTTP protocol compliance entry it says 1 but when you click on it there is no request data. Has anyone else seen this? Is there a retention period for learned entries or a max number that can be stored on a specific ASM? I have 10 or so policies running in learning on this ASM.

Any help would be appreciated.