923+ RAM upgrade modules

Waiting on delivery of a new 923+ with 4 12TB drives.
Do both ram modules in a Synology 923+ need to be the same size? If I put an 8GB module in slot 2 with the original 4GB in slot 1 will it recognize 12GB? Any experience with non Synology ram - will other brand ECC modules function?

Thank you

I just got my 923 in this week. Added 16Mb sim in second slot. It works fine that way.

Up to 64GIG

Update - I went ahead and ordered 2 OWC 16gb ecc modules. Received and installed before installing the HDD’s. Checked the system info and reports all 32gb. Currently running disk checks for another 12 hours on the Ironwolf Pro 12tb disks.