Annex 2 of the Uruguay Agreement of the WTO lists the details of domestic support programs exempt from reduction commitments ("green box" programs). The design of the AIDA program is taken directly from that Annex which states:
7. Government financial participation in income insurance and income safety-net programs
(a) Eligibility for such payments shall be determined by an income loss, taking into account only income derived from agriculture, which exceeds 30 per cent of average gross income or the equivalent in net income terms (excluding any payments from the same or similar schemes) in the preceding three-year period or a three-year average based on the preceding five-year period, excluding the highest and lowest entry. Any producer meeting this condition shall be eligible to receive the payments.
Its all there: three year averages; 70% coverage (100%-30%=70%); NISA clawback ("excluding any payments from the same or similar schemes"), etc.