Question pertains to this host: https://setiathome.berkeley.edu/show_host_detail.php?hostid=7184655

This system has been running mostly trouble free (which is why I hesitate to 'upgrade' to a newer Ubuntu) for a few years now with a single HD7770.
To boost its RAC, I decided to add a second and identical Radeon. It took some fiddling to get it to work, but once it was working, the S@H host information indicated that the cards were something like 930mb each whereas before it showed the full 1024mb on the single card. Well, that didn't bother me too much but then I goofed it up and had to reinitialize the driver for a second time. Now it is saying the cards are 899mb... what's happening?

Thanks in advance!