The valid length for packed numbers is between 1 and 16 
bytes; two decimal places are packed into one byte, whereby 
the last byte only contains one place and the plus/minus 
sign; after the decimal separator, up to 14 decimal places 
are permitted. Depending on the field length len and the 
number of decimal places dec, the following applies for the 
value area: (-10^(2len -1) +1) / (10^(+dec)) to (+10^(2len -
1) -1) /(10^(+dec)) in steps of 10^(-dec). Values in 
between this range are rounded off.

it will display exact value as it is.for ex:1.23456
where as floating point F display the round off value for 
ex:1.2