Section 7 of the 2010 BOMA standards reads as follows:

7 – Measure Gross Leasable Area (GLA)
For each floor of the building, and for each occupant on each floor (including occupant areas that are vacant or undergoing renovation for a future occupant), measure the gross leasable area (GLA) to the following perimeter boundary lines:
• At exterior enclosures, the measure line on the exterior face of the enclosure
• At walls separating adjacent occupants, the centerline of the wall
• At common areas, the lease line
• At all other perimeter walls, the side of the wall opposite from the occupant (GLA) side.
Include kiosks but exclude retail merchandising units (RMUs). Include all mezzanines and restricted headroom areas.

Make no deductions for columns or other structural elements or for occupant voids. Major vertical penetrations that classified as non-leasable area and are fully surrounded by gross leasable area are, along with their enclosing walls, deducted from gross leasable area.
Gross leasable area is entered by occupant on each floor of the building in column G of the Global Summary of Areas.

My question is this. Using the 1996 BOMA standards (especially since they provide a schematic example) the leasable area would simply be to measure the exterior facade for the entrance facing "the street" and then the interior wall face for all remaining sides. Now reading the 2010 standards it appears that the leasable area is now calculated by simply measuring all around the exterior wall face of the entire building. Am I interpreting this correctly? The actual specific example is a stand alone "Toys R Us" building.
I originally measured along the exterior facade for the "main entrance" and then along the inside face of the drywall for the other 5 walls. I have been told that the landlord has stated that measuring all along the exterior wall face is correct. These two different methods make a difference of 1209 square feet. Which is substantial. Any help in this interpretation would be greatly appreciated.