GMAT Sentence Correction (SC) | Re: #Top150 SC: Until 2010, a state tax regulation known as the 80-20 rule

Until 2010, a state tax regulation known as the “80-20 rule” required that condominium associations receive at least 80 percent of their gross income from their tenant-shareholders, and no more than 20 percent from other sources, like ground-floor rent for restaurants.
(Meaning: Some tax regulation required that condominium receive income
>x% from abc, and
<y% from xyz
Such incomes are to to be received in the same way as ground-floor rent is