Why does auto increment jumps by more than the number of rows inserted?
This is not unusual and there are a couple of causes. Sometimes it is due to optimisations the query runner makes to reduce contention issues with the counter resource, improving efficiency when there are concurrent updates to the affected table. Sometimes it is due to transactions that got explicitly rolled back (or implicitly rolled back due to encountering an error).

The only guarantees from an auto_increment column (or IDENTITY in MSSQL, and the other names the concept goes by) is that each value will be unique and never smaller than a previous one: so you can rely on the values for ordering but you can not rely on them not to have gaps.

If you need the column's values to have no gaps at all you will need to manage the values yourself, either in another layer of business logic or in the DB via a trigger (be careful of potential performance issues with triggers though), of course if you do roll your own you will have to contend with all the concurrency/rollback/cleanup-after-delete/other issues that the DB engines work around by allowing gaps).