I think I know what he is saying... I too came from a BB Storm...with "advanced task killer" it will show you an "available memory" of ___. That changes up and down depending on how many things you have open in the background.
As far as I know there is no way to check the flash memory without an application like this. Upon boot up my X gives me a 250ish memory available and after running for a couple of days with other things running I drop to around 60-70ish.
Hope that helps.