The 305 km rule is why F1 races aren’t a fixed number of laps.
FIA regs say a Grand Prix must be the smallest number of complete laps that just exceeds 305 km. Longer tracks get fewer laps (Spa: 44). Shorter ones get more.
Monaco is the only exception: 260 km / 78 laps, because a full-distance race there would blow the 2-hour time limit.
That’s why the lap count jumps around the calendar. From 2027 it drops to 290 km.