Convert character to decimal

All,
I have a character representation of a numeric field whose value is
'0009671180' .
This represents 96.71180.
When I attempt to convert it back to a decimal value, I get the following
message:
Message ID . . . . . . : RNX0103 Severity . . . . . . . :
99
Message type . . . . . :
Escape
Date sent . . . . . . : 18/03/13 Time sent . . . . . . :
16:24:25


Message . . . . : The target for a numeric operation is too small to
hold
the
result.
Cause . . . . . : An arithmetic operation resulted in a value which is
too
large to fit in the target. If this is a numeric expression, the
overflow
could be the result of the calculation of some intermediate
result.
Recovery . . . : Either make the target of the operation larger or, if
in
an expression, choose the precision of the operands in the expression
so
that intermediate value will fit into the intermediate
result.

The code I am using is:
<snip>
D Work_Rate S 63 15
,
,
/Free
.
.
.
Monitor;
Work_Rate = (%Dec(Oh@AirRate : 10 : 5) / 100000);
$Air_Rate = Work_Rate;
On-Error;
$Air_Rate = *Zero;
EndMon;
</snip>

Since I made my work field more than large enough to hold the result, why
am I receiving this error?

Thanks,