Snapshots don't capture modifications. They show the database as it was at the time the snapshot was created. So, in your scenario, if you query snapshot 1, it will show Row A as it was at 12:00, if you query snapshot 2, it will show Row A as it was at 13:00
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability