I searched the entire manual and couldn’t find any reference to use of an angle gauge, even for head bolts or connecting rods bolts - so maybe using angle gauge for torque to yield bolts wasn’t a thing on 911’s of the 1979 SC vintage.
Seriously doubt this would be an angle gauge application- it’s a gland nut on a shock housing, there’s no “bolt” per se except the housing itself; can’t stretch that to the TTY point or the housing couldn’t be used again next time new shock inserts are needed.
Have also seen this notation in my 993 workshop manual, but it definitively references an initial torque value
plus X degrees specifically.
This is the WSM page, and the Boge housing is the only item with this kind of notation:
