For an air cooled heat exchanger with finned tubes, the software I'm using requires a "outside area correction factor". I have not heard of this terminology before. Is it referring to the ratio of the bare tube area to the extended fin area or??
You should really check with the supplier of the software. There are several possibilities that they could be referring to besides the one you mentioned such as...
1. The amount of area that is not available for heat transfer (covered by tube supports, etc.)
2. An outside fouling fouling factor.
3. Some correction factor for a "non-standard" fin material.
Normally (I'm out on a limb here), any decent program should calculate the ratio of outside to inside surface to adjust all the thermal resistances to the the referenced surface (bare or extended surface).