SML readout

Hello everyone,
has anyone used the frient Electricity Meter Interface 2, LED? https://frient.com/pro.../electricity-meter-interface-2-led/
It runs on Zigbee, is compatible with Zigbee2MQTT and runs on battery! Since I don’t have a power outlet near the smart meter, this is a cool thing for me!
I also get values delivered, but they can’t be right! It usually shows something over 6000 watts although almost all devices are switched off!
According to the Smart Meter’s P Info, this doesn’t fit either, because the Smart Meter only sometimes says 300 - 400 watts! Does anyone know the problem or have a solution?
Other solutions have not been of interest to me so far, the Hichi heads are supposed to be good, but I would have to run them on a power bank, where I never know when the battery is empty!

Or does anyone know of a good alternative?