Is there a reason for the specific number 2.1111 blackbyte for 1 byteball?

Why not just 2 for 1.

I think this is because of the denominators. Byteballs can be spent at any amount, not blackbytes. Blackbytes are like money, you can spend only use these denominators:

{denomination: 1, count_coins: 10,000,000,000},

{denomination: 2, count_coins: 20,000,000,000},

{denomination: 5, count_coins: 10,000,000,000},

{denomination: 10, count_coins: 10,000,000,000},

{denomination: 20, count_coins: 20,000,000,000},

{denomination: 50, count_coins: 10,000,000,000},

{denomination: 100, count_coins: 10,000,000,000},

{denomination: 200, count_coins: 20,000,000,000},

{denomination: 500, count_coins: 10,000,000,000},

{denomination: 1000, count_coins: 10,000,000,000},

{denomination: 2000, count_coins: 20,000,000,000},

{denomination: 5000, count_coins: 10,000,000,000},

{denomination: 10000, count_coins: 10,000,000,000},

{denomination: 20000, count_coins: 20,000,000,000},

{denomination: 50000, count_coins: 10,000,000,000},

{denomination: 100000, count_coins: 10,000,000,000}

That's how 2.111x10^15 come from.