A Little Goes a Long Way
If you have never used dry shampoo powder before it can take several times experimenting with the product to learn how to use it correctly. A very small amount of the product is needed to achieve the goal. Fine, thin hair will need less of the product while thicker hair may need more. Hair that just started to get oily will need less of the product, but if you wait longer you will need a little more.
"The bottle may seem small, but I need such a small amount that I can't even predict how long this will last for me. (I ordered my first bottle many months ago and it's hardly made a dent...I assume I'll get 6+ months out of this. It's already lasted longer than some spray formulas.)"