My assumption would be that the board says it supports 2GB, and standard metric prefixes denote GB as 1000, not 1024- so the maximum as they see it is 2000MB.
Additionally, RAM is sold with markings indicating their size in MB; in this case, 1024 for the 1GB.
Thus, they come up with RAM that is 2048MB, and the board maximum of 2000MB.
Just a wild guess; but it is likely the case.