select * from [dbo].[Customer]
where IsSystemAccount = 1
Query should return two records. When site get crawled, system consider the bot as [email protected]_engine_record.com instead of creating new customer records(eventually increasing identity value).
If you already have the system accounts, check if you have any third party monitoring system (like monitis, pingdom) setup to do automated testing on your site which can create guest customers and increase identity, in that case you need to modify code to assign the testing tool as a system user.