The US Mint lists this for the American Gold Eagle quarter ounce Since there is no household limit can you explain this difference.
I think montage refers to how many coins. The coin may be available in different products (individually or in sets).
The mintage limit is the total number of coins, so for the 2013 quarter ounce gold proof the maximum total mintage possible is 30,000 coins. The product limit is as follows 10,000 of those coins will be offered as single packaged quarter ounce gold proofs and the other 20,000 of the mintage limited to being contained within the 2013 gold American Eagle 4 coin proof set.