That's what cron shows for me too. 5 and 1/4 inch diameter. Assumes it was ripe enough for you to eat close to the rind. Try an experiment just once and weigh the edible part and see if it matches up.
Are you in Europe.
The honeydews in the U.S. are much bigger and totally different to the ones in Europe. I assume that cronometer uses the U.S. ones.
They taste different as well and must have different nutrients.
You must be in Europe as you could not possibly eat 5 on the U.S. ones.