Unreal Engine: Now Available to Everyone for Free

I would be nice for Epic to clarify about $3k per quarter thing. Does it mean that each quarter separate cycle? For example, if I make $5k first quarter and $2k next quarter and $3k the following quarter, would I only pay 5% off $5k gross (or $2k gross?) for the first quarter only? Or since I made (hypothetically) $5k gross in the first quarter, I have to pay 5% for the first quarter and on ?