The trinket has procced, and the cooldown is showing on the trinket slot. The number is provided by CooldownCount. InternalCooldowns is compatible with mods like CooldownCount and OmniCC.
InternalCooldowns provides CallbackHandler hooks, so you can display the cooldowns on procs in most any form you like. Pictured is the Egg of the Mortal Essence proc on the Forte Cooldown bars.
InternalCooldowns can report when your trinkets can proc again to your scrolling combat text display.