ITH-10 Hygrometer

Does anybody know how to adjust the calibration on the ITH-10. It is off by 5% humidity and Inkbird refuses to answer my question.

Sorry, the ITH-10 does not have a calibration function.
The humidity reading accuracy of the ITH-10 is ±3%.
Could you please use the salt method to test it?
Please put the ITH-10 inside the baggie.
Here are the details:

  1. Gather supplies. To test your hygrometer using salt, you just need a few household supplies:
    A small food storage bag that zips
    A tiny cup or bottle cap from a 20-ounce soda
    Some table salt
  2. Fill the cap with salt and add enough water to make a thick slurry. Don’t add so much water that the salt dissolves; you just want it to be wet. If you add too much, use paper towels to mop up the excess.
  3. Put the cap and the hygrometer inside the baggie. Zip it up and place it somewhere out of the way, so it won’t be disturbed during the test.
  4. Wait 6 hours. During this time the hygrometer will measure the humidity inside the bag.
  5. Read the hygrometer. If it’s accurate, it should show a humidity of exactly 75%.

Reference link: How to Test a Hygrometer: 6 Steps (with Pictures) - wikiHow
Can it read 75% after 6 hours?
If its readings still deviate significantly, please contact the seller/ for after-sales.