These codes stem back to the "Old School" days of AutoCAD in DOS, but are each still useful today. All of these codes still work with DTEXT using the standard AutoCAD fonts. Likewise, all but the %%u and %%o codes work with the newer MTEXT.
%%d = degree
%%c = circle diameter
%%p = plus/minus tolerance
%%u = begin underline of text. Repeat to end underline.
%%o = begin overline of text. Repeat to end.