Hi, the 1M threshold is lifetime.
The moment lifetime revenue goes over 1M, royalties kick in on any revenue over the threshold.
The basic formula is: (Lifetime Attributable Gross Revenue) - (1,000,000) * (0.05)
In addition to this there is also a quarterly minimum - You only report and pay royalties for a quarter in which the quarterly revenue was >10 000$.
We have a great talk at Unreal Fest next week that digs deeper into some of these details. At some point in the weeks to come we will have the video of that session go online. That should be a welcome additional resource.