That's OK, just don't overdo the calibration, it won't be like a multimeter.
For calibration, I need a more or less accurate laboratory power supply and a functional signal generator, which I don’t have.
If you don't want to spend much, I purchased a cheap device like this one https://www.aliexpress.com/item/1005006786894152.html it comes with a hand written paper with the real measured values with good equipment and also states the date and temperature when they were done, it can be used to know how good are the measures of your equipment.
That's certainly nice, but only DC (afaics) and you don't really need that kind of accuracy for the scope.
An average multimeter is perfectly adequate as a comparison.
The scope only has to display approximately the same as the multimeter. So not exactly 1.0000V but e.g. with a battery 1.5xV or 9.xxV
But Autocal is also sufficient imo.
By the way, an FY3224s also has a DC mode and you can output -10V to +10V DC. If you compare this with a multimeter, it should be accurate enough as a reference for the scope.
Of course it can do sine, square etc. anyway.