A/C System Refill Issues

[Oka]

I am in the process of recharging my AC system. It's not that cold inside the car.
From the vent at full blast, I get 48F.

With car stationary and running in full blast, the compressor engages and disengages
in ten seconds intervals. When driving, it does not seem to engage and disengage.
Isn't the ten-second intervals abnormal; the intervals are also consistent while stationary.

I have AC/Pro refill cans. With my readings, I could not fill the system with the
refrigerant with UV so as to use the black light to search for possible leak. So, I do
not know if there is a leak somewhere.

Thanks in advance.