You are attempting to change a database column of type decimal from a precision of two decimal place to one decimal place via data annotations, and there does not seem to be a good way to do it.
There isn’t a good way to do it.
However, there is at least one non-elegant way to do it – in your OnModelCreating code in your data context, enter in the following piece of code
protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
The “HasPrecision” part is the key – the second parameter is the number of decimal places to use