I read only the other day that one of the advantages of vxfs being an extent-based filesystem is that it does not have a limited number of inodes, it is only limited by the amount of space you have for the filesystem.
Having said that... you can see some figures in df -i showing the current and maximum number of inodes, even for vxfs filesystems... so I've no idea what those figures are based on.
Annihilannic.