Tennis Betting Wizard is based off of a YouTube video from a fairly well respected gambler that has a twitter following in the thousands. I discovered his video on an underground betting community that said his method of tennis betting worked better than most of the paid ones that were out there. However, I found his system to be a bit limiting because he had you combine the (surface) and (vs opponents of similar rank) into one which gives you a small sample unless the player has played a considerably amount of matches that year. It also leaves out a pretty important metric which is if these players played in the past 52 weeks, who won? That can't really be ignored. My tennis betting calculator weights each of these three factors equally.
It then calculates the most probably winner and gives you the "confidence" in it's pick which is the gap between the two probabilities. Any number over 2 is considerable. However, I don't have a strong recommendation for what a good confidence is at this point. You might want to use this calculator as part of your own system and come up with your own beliefs on what a good confidence number is. When we get more feedback from the community I might update this and offer a recommendation, but for now I say I come up with your own system, and if you want help in doing that we've started a subreddit here: r/TennisBetters.