DbSet in Entity Framework
There are many things that can cause gaps in an IDENTITY column (rollbacks, deletes), but in this case due to the jump I suspect it is this bug - caused by the changes to IDENTITY with the introduction of SEQUENCE:
We know that Entity Framework can generates keys using either the IDENTITY or SEQUENCE (SQL Server 2012) features
EF Core Support for Blazor Our Blazor Server UI and our Entity Framework Core ORM classes were first introduced in October 2020 (as a community technology preview - CTP)
The same happens for any autogenerated key values, including the commonly used auto increment (identity) columns
In some rare cases, the standard incremental nature built into the SERIAL and BIGSERIAL data types may not suit your needs