I suspect your resulting field is of data type integer or long, neither of which can contain decimal portions of a number. Your results also look like text as they appear to be left justified but can't tell for sure. Try entering the value you expect directly in the table and it probably won't work. Change field property to Double, save, then try editing again.
I can't think of a reason why you cannot edit the other thread. Site is very slow lately so maybe you didn't wait long enough when you tried. We're also getting time-outs on page loads.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.