why is my teacher asking me take out 10ul of solution from my solution bottle for serial dilutions and not from my sample?

Question

So my experiment was that I will have e.coli bacteria in a spray bottle to spray onto a tile surface and too see how many bacteria were transferred. I then swabbed it onto a plate. My teacher told me as the plate had too many colonies id need to dilute it . So she said that I will go into the original spray bottle and scoop out 10ul using an inoculating loop. I am confused why. Am I not suppose to take out a scoop from my plate as thats what I want to dilute? is she assuming that when I sprayed my solution from the bottle, around 10ul was sprayed out onto the tile surface hence taking out 10ul from my solution bottle??

Answer 1

Your sample concentration is to high. Your bottle solution is less concentrated. I assume the solution bottle concentration is known and it would have less colonies. 10ul to another bottle with solvent,would make it less concentrated with less colonies.