He's likely referring to the cards for Kana and the catalysts for the MCs. All Catalysts have an element, which is random, the possibility of a secondary element of sorts, which is also random, and which stats they have are, also random, though the values are only semi-random because they depend on the overall level of the location you get the catalyst in.
Likewise, with Kana's cards, the type is random and the stats on them are semi-random. Though it's not as much as with the catalysts, because the cards have somewhat specific stats for each type, and then there's no proper randomization when mixing them.