[Fortification]

Hello! I just wanted to ask a quick question...I've looked in my Chemistry books and searched the internet and this site but I'm not able to find out what this symbol means:

Delta H (which I understand) and then it says at, in the place where it normally says f or c for formation, combustion etc.

The sheet which I've been given is handwritten though so I'm not sure whether it actually is at or just illegible. Anyway, thanks in advance for any help.

[enahs]

You did not describe the symbol or attach a picture.
You said where it occurs....After the ?