verbiage for repair..

[Tom Server]

So, looking to purchase a co-op and the co-op is offering a credit towards replacing the floors. 

"Buyer to receive $5000 credit at closing, Buyer agrees to replace subfloor with 3/4 plywood, mildew resistant and sound proof flooring insulator"

Obvious labor is expensive, What are your thoughts on this.. the actual subfloor is fine but its in the contract to install new subfloor anyway

with the "replace subfloor", could I install new 3/4 plywood over the existing subfloor which technically i am replacing the subfloor or do i need to discard the old subfloor and install the 3/4 plywood??  

thoughts?