Because Bitmart has the bid and ask and one may be the bid and one the ask on the last trade registered on each site. On my computer both sites show 13 zeroes 14. Bitmart updated automatically. Coinmarket cap I usually refresh.
I just started a new crypto board to talk about cryptos, especially micro cryptos, where millionaires can be made, just by losing some zeros. Just search Micro Alt Crytos or Let's Lose Some Zeros or link in my profile. Come pay a visit. Brand new.