No worries, it's a simple fix. The lost+found folder contains a bunch of junk, and that's what's taking up all your space. My GS2 also had this problem.
rm -rf lost+found
Nook Color running CM7 Mirage, no gapps, Nook Tweaks app @ 1.3GHz (+500MHz past stock 0.8GHz)
Nook Tablet running CM10.1.3, no gapps, BexusNv4 kernel @ 1.3GHz (+300MHz x2 past stock 1GHz)
SGS2 T-Mobile (unlocked) running HellyBean 4.2.2, no gapps, @ 1.72GHz (+~200MHz x2 past stock 1.51GHz)