That's not unusual. Almost every standard grind knife I own has (no, had) different angles on each side. One might be 19 degrees, the other 22. You can use a diamond stone as mentioned above or......
Start with 320 wet/dry, then 400, and finish with 600. Cut the paper along the 8" edge, strips about 1-1/2" wide. Lay them face down on your bench, center one of your triangle rods on it, and crease one the edges (crisply!), folding that edge up one side of the rod. Then, maintaining pressure, lift the other side and wrap it around, making sure to crease that edge too. The idea is to wrap the rods with the 320 grit tightly so the faces are clean without any bulging in the corners. Using small spring clamps (or maybe clothespins,,,maybe) put one near the bottom and one near the top to keep the paper clipped to the rod. You'll have to slide the rod down out of the paper about 1-1/2" at the bottom so it'll go in the Sharpmaker hole. Do the same to the other rod. What you have is your Shaprmaker with 320 grit wet/dry on the faces.
Now you can work your edges to 15 degree or less. If you put a 1/4" spacer under one end of the Shaprmaker, you'll raise it and decrease the 15 degree (30 deg holes) to 12-1/2 degrees. You can use a protractor and play with it to get it right. Just remember to switch the spacer when you switch to the other rod for the opposite facing of the blade (DONT axe me how I knowd that!)
If you take 20 swipes or so per side, wiping the wet/dry with water on occasion, you'll re-bevel the edge where you want it. Depending on the steel, you may have to reface the rods a time or two before you're done.
After going through the grades up to 600, you can remove them entirely and go to the medium Sharpmaker rods. If you used the spacer, you'll have about a 25 degree (inclusive) bevel on your edge. When you go to bare rods, you could remove the spacer and then create a microbevel at 30 degrees.
I've done that with almost every std grind knife I own. Now, both sides are equally ground on all knives. Good luck
