That fraction is going to depend a lot on the definition and the reference. I believe the 97% is the US standard for how much of the natural caffeine in green beans must be removed. You will note how this can be manipulated by using a more caffeine-abundant variety. EU standards are more sensible, stated in terms of caffeine content in the final product.

Either way, commercial decaf processes and normal brewing methods will yield something like 5-10mg of caffeine in a "decaf" dose of coffee, which is an order of magnitude less than usual.

The bean is already only like 2% caffeine lol so cheap decaf can definitely really be "half caf" even if they say that.