Beckhoff EL6751 RxQueue size

I'm aware that it's a "RTFM" question, but I've been reading for two hours and I can't find the answer...

I have an EL6751 CAN Interface, working fine.
The receive message queue has 5 messages.
I believe I have to increase this size because I am missing a significant number of messages that can come in in bursts of up to 20 messages in 3ms.
I can see the queue in TcXaeShell (capture attached), but I can't figure out how to increase it.

Anyone has any idea? hint ? suggestion ?

Screenshot 2022-12-13 163630.pngScreenshot 2022-12-13 163704.png