The actual breakpoint for WG14 with a 70% SotF would be 3421. You're conceptually right but there's some rounding in-game that's not obvious--the tick interval is rounded to the nearest millisecond before the number of ticks is computed.

At any rate, SotF is currently 75% on PTR. That will give the 14th tick at 2109 and the 15th at 5437.