"Ready to depart in 3 hours" for reserve assignment. You also get 15 minutes to call back once scheduling calls to notify you.

it isnt 3 hours to show.

From the ALPA NewHire guide for reference:

"Our SCR “callout” time frame is often misunderstood. The requirement is that the pilot be ready to push no more than three hours from notification, not necessarily the aircraft ready to push. We advise that a pilot arrive with enough time such that the required duties and safety checks for which he is responsible be accomplished within three hours from callout.
Example: A pilot on R03 can be called at 0300 for a 0515 report (0600 push)."