The High threshold boxes contain an upper limit (in the appropriate units) on the current temperature above which no further thermal compensation will be applied. PC-DMIS doesn't display any warning or error message.
With a reference temperature of 20 degrees C, a current temperature of 35 degrees C, and a high threshold of 30 degrees C, the amount of correction actually applied would be based on a difference of (30 – 20) instead of (35 – 20) because the current temperature exceeded the upper limit.