In one complete oscillation, sin(x) starts at 0, goes up to 1, then down to 0 and continues down to -1, then back up to 1.

10 sin(6pi t) will start at 0, go up to 10, down to -10 then back to 0 in one complete oscillation. "One complete oscilation" will occur as 6 pi t goes from 0 to 2pi which means as t goes from 0 to (2pi)/(6pi)= 1/3 and points with d value 0, 10, 0, -10, 0 will occur at quarters of that- when t is 0, 1/12, 1/6, 1/4, and 1/3 respectively.