Decimal 4, 4 allows for 4 digits, all 4 to the right of the decimal. So it stores values between 0 and 0.9999 (on the positive side), but it cannot store 1.0000 as that requires 5 digits, not 4.
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