This is completely incapable of measuring individual milligrams. Just because it claims to and shows a digit for it doesn’t mean it can.
Even $500 analytical balances like [0] can struggle with 1mg resolution, but I’d trust them a lot more. Generally you need to throw away the least significant digit of precision with digital scales.
The request may have been misguided. They don't need a milligram accurate scale. They're actually wondering how to taper a 10mg doses drug, which is actually comprised of a much higher than 10mg pill, more like 100 to 200mg. The rest is typically binder.
Also, note that while your $500 scale may be necessary for absolute accuracy, splitting 10mg is not the same as finding exactly 10mg.
There's a few modernist cooking tricks that require small amounts - tenths of a gram - for big impacts. Sodium citrate can make any cheese melt beautifully into a smooth sauce, using something like 1% of the weight of the cheese.
Any juice can take the roll of lime or lemon (in cocktails or baking) by adding a bit of citric or malic acid. Orange juice is 1% citric acid, so add 3g citric and 2g malic per 100g juice and now you can make an orange daiquiri or "key" orange pie.
Emulsifiers get goopy if you use a lot, but can make a smooth syrup in small amounts. You can make a nice syrup from any nut milk with a small amount of xanthan and gum arabic.
There's a wide array of ingredients including xanthan and gum arabic used in tiny amounts in gluten free baking
I sometimes wish my scale was precise to below 1g when measuring yeast for long-rising (bread) dough. A recipe may ask for 1g, and adding 2g will make a huge difference.
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They're common, cheap, and plenty of (recreational) drug dealers use them.