The TG124A is only rated to -15 dBm. The TG44A goes to -10 dBm, though.
We do test each unit at their rated output power. It’s a tricky test, because we measure harmonics (which can be high), and then total output power with a thermal power sensor, and then calculate power at the fundamental frequency.
We do guarantee their accuracy (e.g. -15 dBm at 100 kHz should read -13 to -17 dBm on a suitable RF power meter). If you can make an accurate measurement at the RF output connector, and it is out of tolerance, this would be covered under warranty.