70% rule Vs the fix and Flip calculator

[Wayne Griffin]

lets say the ARV of a property is $320,000 when I apply the %70 rule I get $320,000 x %70 = $224,000 - profit of $50,000= $174,000 - repair $63, 860 = $110,000 purchase.

However 

When I use the Fix and Flip calculator it suggest that my purchase price should be $155,940 as my maximum offer.

why the difference of $45,800 please advise