Your whole bathroom doesn’t have to be the temperature. The chicks just need to have access to heat that they can get to. That’s how the brooder plate works. It does not have a temperature setting, if you feel under it you can feel that it’s quite hot. I don’t know this brand, but it should be adjustable in height so that you can change the height as the chicks get bigger. I use the Brinsea models and the height is adjustable. I usually make the backend a little bit lower and the front end a little bit higher so the chicks can decide how much heat they want. I use converted chinchilla cages, I have some covered with plastic on the side to prevent drafts, others I drape a towel over the back end of the cage where the brooder plate is. Just like in nature they go to the mom for heat but then they venture out periodically and then just go back when they feel like they need to be warmed up. I do find the first night or two I have to stuff them under the heat as sometimes they’ll venture out and not be able to figure out how to get back under it when it’s dark. Once they figure it out then there’s nothing to worry about.Well i just got a brooder plate but it doesn't have a temp to know what it is...just says brooder or heater.
So I have been struggling all day long trying to get 99.5 even in a confined tiny bathroom.
It's this Producer's Pride Brooder And Coop Heater and in using it as brooder currently.

Here’s a few photos that show the brooder plates in action.