When I initiate a replay on my queue, why do I only see 1000 messages get replayed?

hong

When you initiate a replay on your queue, you may notice that only 1000 messages get replayed. You know that you have way more than 1000 messages matching your queue subscription that you should see. This is actually expected if you have no clients bound to the queue at the time of the replay. When clients bind, and as these messages are consumed, more messages will be replayed as replay resumes.

RunningRoach

I think this might answer your question:

Limits on number of messages sent in a replay request

• If a replay is initiated to an endpoint that has no clients connected, only 1000 messages are replayed. This ensures that the unacked resources of the endpoint are not completely consumed.
• If there are connected clients, the number of messages replayed is limited only by the max-delivered-unacked-msgs-per-flow setting on the endpoint (up to 100,000 messages).

https://docs.solace.com/Features/Replay/Message-Replay-Overview.htm