@Override
	public Step subtract(Step step) {
		assert isCompatible(step);
		SkipStep that = (SkipStep) step;
		return new SkipStep(this.threadKey, this.tickCount - that.tickCount);
	}
Construct a skip step for the given thread with the given tick count

@param threadKey the key of the thread in the trace, -1 for the "last thread"
@param tickCount the number of ticks to skip on the thread
Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/time/schedule/SkipStep.java