That is right. With premium program you can earn up to 5.10% (+1.02%)* annual interest.
The method to raise your interest from 4.08% is by investing in the FUN tokens? I am currently running my coins on the base interest of 4.08% and any boosted amount is always welcome. I thought the FUN token investment was a separate scheme altogether, meaning that two investment schemes were running on the site side by side - correct my if I was mistaken.