Here's the telegraph and the speed that we are talking about. Red means reverse.
停止: Dead stop.
微速: Slow speed, 6 knots or so, for port maneuvers and whatnot.
半速: Half speed.
原速: normal speed, base cruising speed, usually 15-16 knots
強速: high speed, increase by 2-3 knots, close to 20 knots or so here.
第一戦速: First combat speed:
第二戦速: Second combat speed:
第三戦速: Third combat speed.
第四戦速: Fourth combat speed.
第五戦速: Fifth combat speed.
最大戦速: Max speed. 35.5 knots on the Kagerou class
一杯: immediate overboost. Melt the boiler.