I may has missed something on the Hercules site, but it looks like that they don't have a MX400 which is 64 Mb, they do have a standard MX though.
The boot up screen is OS inderpendent, thus if it says there is 32 Mb then there is 32 Mb
The way I see it there are 2 options
1 - You have a MX400 in a MX box
2 - You got a MX400 with 64Mb ram (If so can you tell me where), and board has been damaged.