Alright, let me get this straight. I'm assuming they notified you of your L2 yesterday or a few days ago. So, today you are on L2 (0700-0900 & 1700-1900). They called you this morning at 0855 to notify you of a 2100-2400 ready reserve. Now, if I read the contract correctly, your ready reserve has to fall within your reserve window, which is 1700-1900. 2100-2400 does not fall in your reserve window. If they would have changed it to A6 or A7, then it would make sense.

Someone correct me if I'm wrong. Unless there is some loop hole around this L2 for ready reserve this assignment is illegal.