Shanks’s 4,048,900,000: 4890 – Shanks (4=shi 8=ya 9=ku)
Big Mom’s 4,388,000,000: 8800 – haha = mother (8=ha)
Kaido’s 4,611,100,000: 1110 – hyakuju = Beasts (100=hyaku 10=ju)
Whitebeard’s 5,046,000,000: 4600 – shiro = white (4=shi 6=ro)
Gol D. Roger’s 5,564,800,000: 6480 – Roger (6=ro 4=ji 8=ya)
The current Yonko’s bounties (4 Billion) refers to the “Yonko” being a meaning of “4”
Then there’s prediction about Luffy’s final bounty going to be 5,600,000,000 because 56 = Gomu (5 = Go, 6 = Mu). This is referring to Luffy’s Devil Fruit, Gomu Gomu no Mi.