17dBm + 2dBi = 19 dBm
your EIRP (radiated power) = 19 dBm
it’s as simple as that 🙂
I assume it is an omni directional antenna ? in this case, in all 360 degrees, there will be a TX power of 19 dBm.
In case of panel antennas, only in the main direction of the lobe will you have 19 dBm. In other directions, you must include a certain attenuation (check the antenna pattern).