Product review (1 stars): It's junk, and not returnable.
This device is available from many different sellers under different product names.  I have 2 from other vendors that seem fine.  They all look similar but this one is junk.  If you touch it or move it, the temperature swings from say 78 to 103.6 then down to 54.3.  When it finally stabilizes, it reads about 4 degrees too low (compared to more reliable thermometers).  And the other reviewers are right -- the instructions are worthless.  I got it set by trial and error.

It cannot be returned.  Not a great tragedy since it was cheap, but still an irritating waste of money.

Avoid the grief and look elsewhere.