That's a good idea but I already ordered a milligram scale. Though the scales should be easier to make adjustments, and will be used for measuring seeds and other smaller food stuff.
One thing I am not 100% sure on, I think due to 'marketing'.
For example the Magnesium Glycinate says 2200mg per serving but then amount per serving is 400mg.
This made me think that 2200mg was the Magnesium amount at first but now I think it's just total weight of the serving. A bit of annoying marketing.
Don't over-think this. Magnesium Glycinate is fine if you'd rather substitute that, it's just a lot more expensive.
It doesn't need to be so exact. Just as long as you're not pouring in an insane amount of magnesium and potassium you'll be fine. That's why is 1/2 tsp per 2 liters, because it's designed to replenish your minerals/electrolytes from not eating whatsoever. If you are eating normally (2-3 meals a day) and drinking this, which I wouldn't recommend unless you're dehydrated, or lifting heavy weights, then you can cut this recipe down to half or 1/4 of what it is.
This formula is designed for full-on fasting without eating. It is designed also for those on Keto to avoid the "Keto Flu" and headaches and stomach cramps.
You certainly can drink it and eat normally, but as I said, it is better to scale it down.
Do not chug this like you just ran a marathon either. It's for sipping periodically. Small sips, so your body can absorb the salts and minerals.