IP off by one digit

[TechDummy]

I just received an email from a service I'd recently registered with, saying they detected a login from a new device, and showed the IP address, which was almost the same as the one that this site showed for the same session on the same device, but it was off by one digit. Is this a common thing? Just wondering. Thanks for any information.

[Chrispcritters]

It's not unusual for the IP address of a smartphone or residential internet connection to change now and then.