An old Corolla, is it using R12 or R134a refrigerant? 10c at the vent is ok. Did you put the fan on recirculate and test while the car is moving? If not, try again.
The vent temp is calculated on many factors so a tech would not give you a definitive answer to your question. The only way to assess your ac system is by checking the superheat.
Take a look at the chart below.