Might want to ask the boss to verify, but a wave graph usually refers to a sinusoidal shape. In this case, I'm guessing it shows the up/down of the wins and losses. The tendency could be calculated several ways, but I'll take a guess at a straight linear interpolation. Given that vague description from my boss, this is what I would have produced.
It's a line graph with curved lines. I use a double layer of axis labels to get the years and win/loss labels. Added a linear trendline. Hope it helps!