Member percentage interest in condo used to calculate sq ft - Doesn't match actual

[Laura Casner]

Condoized mixed use landlords: I could use some help navigating the complexities off member percentage interest sq footage vs actual. 

The sq footage of the unit is listed as 1351 and a previous appraisal was based on this.  The 1351 number was calculated by the initial developers as member percentage interest 3.9% of the total sq footage of the building: 34,648 and that's what the appraiser went by. But the actual measured sq footage is 1,116 (exterior to exterior) which is quite different.   

My question is - when it comes to renting out the space and charging a price per sq ft., which calculation is it legally and customary to use? The member percentage interest calculation or the actual measured sq footage? I thought the member percentage interest was used predominately to calculate NNN costs/pro rata share and not sq footage...