Try a drop or two on some baking soda… if it bubbles then it’s acidic, use with care.
If it doesn’t bubble then it’s Water with Calcium fully absorbed.
Can you use it? I do… There is an input for Brown Rice Vinegar and I treat it as part
of the WCA that isn’t completed and don’t add any of that input.
4ml per gallon isn’t too much, go for Half and give it a try.