Having 10MB as the target number does not mean that the log will shrink to 10MB, only that 10MB is the minimum. If say the log has 25MB of log records in it, then it can't shrink to 10MB.
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