Newbie composter question about REOtemp thermometers

I just started my own compost pile about a week ago. Yay!
I bought a thermometer to check it's temp. I've never used one of these contraptions for compost before lol.
How long do I have to keep it in the pile to get a reading? Do I leave it in overnight? A few hours? Or is it made to read it within a couple minutes?
Forgive the silly question, but I am so new to this!
The thermometer is a REOtemp 20 inch long stainless steel rod, not digital or anything.

It'll give you a reading in a couple of seconds, unless it's busted.

Thankyou! My pile is very new so it's only reading 70 degrees. Hope it rises soon! I mixed in shredded oak leaves, horse manure, UCG's, straw, and some pine needles left from winter mulching. I need grass clippings I'm sure, but that'll have to wait as it's been raining like nuts the last couple days. My grass is lovin' it though!