What does “Current period” mean in Cellular Data usage

On my phone, I have to reset the cellular data on my billing date if I want it to reflect my usage from the billing period. As I have unlimited data, I've never done that so "Current Period" is at least as long as I've owned the phone (don't know if data carried over from the last phone).

I've seen other people report that there is some sort of automatic carrier reset. So, perhaps it varies by carrier.

Are you sure if you’re the only one using your hotspot? You should click on the button in cellular that says personal hotspot and look at what devices have used it

Thanks for that tip. I've been troubled in recent days by enormous data consumption by unknown users/apps.

However, when I go into Hotspot in Cellular, it breaks data usage into my laptop, another address, and the vast majority of data attributed to 'Other devices'. Is there any way I can find out what those 'other devices' are?

It won’t it will however carry from the SIM card if you have used the SIM card in another phone

"It won't it will" is a bit confusing. Do you mean that it won't unless you move the SIM?