When you look in the Login tab, it shows everyone who has logged in so, for example, when filtering by a year group, you may not get all learners. Also, if the learner has logged in with their username and their email address, they may show more than once:
This doesn’t mean they have two logins. You can see this by clicking on Column visibility at the bottom of the load user accounts table and then click MIS ID. You will be able to tell if it’s the same person if the MIS ID number is the same.