Hi Mumu,
as I know for now, 34 of 64 ESA channels are reserved for audio connections between Mixracka and the Surface. Channels from 1 to 32 are transmitting audio signals from in/out cards and channels 63 and 64 are used as a PFL line. So only 30 of them are free to assign.
But it is possible in some way to use 62 channels, but I don’t remember how I did it. I had to use two iLives, one with ESA and ESB and the second with only ESA. I split 62 signals through Ethersound.

THERE IS NO JUSTICE, THERE IS ONLY ME

Hi Dave.
As Mr B says, simply touch the number box to highlight it, then turn the rotary encoder to scroll through the numbers. You can assign channels 33 to 62 on the ESA network. 1 to 32 are used for the four option cards on the rear of the surface, and 63/64 transport the PAFL monitor signal to the surface. That gives you 30 additional channels you can send along the ESA network, for example to an EtherSound recorder or to EtherSound break out boxes to give you analogue or other digital feeds to a multitrack recorder.

For each of the ESA 33-62 channels you can assign its source from the OUTPUTS screen. You have many choices including channel direct outputs, mix outputs and also mixrack inputs (the signal immediately after the preamp, typically used for live multitrack recording).
Hope that helps,
Carey