BTC to Bytes: every 160 BTC gives you 1 GB from the distribution (or 0.00625 GB per BTC).
Bytes to Bytes: every 10 GB of existing balance gives you additional 1 GB from the distribution (in other words, +10% to existing balances).
Similar ratios for blackbytes.
For those who receive their first bytes from cashbacks, Sep 6 will be the first distribution when they receive +10%.
I'll make announcements as we add merchants in the cashback program.
If my calculation is correct, that's about 7% worth of return (not including the +10% of 10gb existing balance).