How to Calibrate ZOYI-300 AB?

[masterwizard43]

A few days back I perchased ZOYI-300 because of its Bluetooth feature, and thought it is cool. I got it for around 35 USD.

Every feature works great, it even has "Auto" Mode which works reasonably good. But. It's DC voltage measurements are off by more than 1%

On average this DMM showing about 1% more than  the actual values.

I feel bad throwing away this meter, and want to somehow calibrate it. This meter looks the same as aneng 9002 and i think they are the same. It would be great if anyone can guide me how to calibrate it. Thanks 👍

[masterwizard43]

Ohh and, here is how it looks from inside
https://photos.app.goo.gl/L62oK8e5n17UNDYW9

Front view
https://photos.app.goo.gl/Pf6pAhKvpSE268v6A