It seems to be a very limited DMM, but also a calibrator for other equipment, which would be it's main function (hence it's name).
Calibrators are supposed to be high precision devices, so you can rely on it.
You'd have to question yourself what level of precision a $ 40 device would be (even if it's at it's normal price of almost $ 100).
The "24 v loop thing" means it will supply (a hopefully reliable) 24 volts, and will measure the current your sensor sends, 0 - 20 mA is an industry standard, there's quite some sensors that can be set or have such an output.
For it to function properly, you'd have to supply a (24 volts) power to that output, and for the measurement to function properly, your supply have to be reliable enough.
So this calibrator can also be used to test said sensors without having to set up a supply.
It's a bargain at that price, but "(0,2% + 4)" precision for most ranges doesn't impress me much for a calibration device.
1 sold and no reviews doesn't help, OTOH it might be new to Aliexpress.