Yeah, that's why I have doubts. I think Level 5 is the best for 4.5 days ROI but I can't trust the site to live in 5+ days. They need to get Level 6-7 investments, otherwise they have to shut down before expected time.
You'll need only 4.08 days until ROI for Level 5.
For Level 6 you need only 3.86 days.
If you find somebody, who will let you participate on his Affiliate fee, it could be a little bit faster

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Right now there is a big problem with refback offers because affiliate statistic doesn't show you your referral commission but only your referral's current balance that means almost nothing (it becomes zero every time your referral withdraw money).
You cannot calculate total earning from this particular referral.