Requirements for filing Form 3520

Hi!

I am trying to understand if I need to file a Form 3520 for a real estate gift which has a basis of $40,000 and an FMV of $250,000.  I understand it is only necessary to file From 3520 if receiving over $100,000 (or that worth).  Is that $100,000 determined by the basis or FMV? 

Thank you for any help with this!