The “compounding effect” usually refers to interest earned on money.
It’s the principle of reaping huge rewards in the long run from a series of small gains in the short run.
The same can be applied to work ethic.
If you work 15% harder than your competitor every day, for seven days, then you will effectively have worked an extra day every week, an extra 4,5 days every month, and an extra 54 days every year.
Every extra effort you put in compounds on previous efforts, and makes for a cumulative effort which over time becomes unbeatable.
Keep working harder than everyone else.
It has a compounding effect.