I bought a car inverter (150W.) The inverter output should be 220V 50Hz (in Turkey) but the output is 227V 46Hz. I think the voltage is at a reasonable value but is the frequency OK? I measured the values with the power meter. When I measured the normal home socket with the same power meter, I saw 222.5V 50Hz.
Obviously your inverter is a cheap inverter that only outputs an AC frequency that is only approximately 50 Hz but not exactly.
You need a more expensive ("pure sinewave") inverter to get a more accurate 50 Hz.
The fact that you the frequency isn't exactly 50 Hz is only a problem with devices that rely on the 50 Hz to be accurate because they use the 50 Hz as a reference for timing.
Some motors need AC to make them spin, if the frequency isn't exactly 50 Hz the motor could spin too slow or too fast.
Examples of such devices are clocks and maybe some older televisions.
Devices that are unaffected are devices that rectify the AC into DC like power adapters and chargers. Some devices state that they can use 50 / 60 Hz on the device itself, also these don't care much about the exact frequency.