Head may be mispelled, or hhea may be a typography term I am not familiar with.
Again, I am not trying to be critical, the program is great, and I've just finished creating a font that meets my needs. I ran into some unexpected behaviors, but I was able to figure out TypeLight wanted me to do, so I got over it. (some symbols got "linked" and modifying one, changed others. This may be a useful feature, but I did not expect it. I did follow the advice to may frequent backups, so it was not a big problem.)