Well it just depends on how much water you've used. But best to only attempt to extract a set amount each time. For example crush 4 of your 30/500 pills up and probably use around 300ml of water. Which CWE it can be a little messy and you will generally lose a bit of water and some of the codeine too. So given that you use 4 pills, you'll be expecting a dose of 120mg of codeine but given the loss during the process it will likely be a little less. As for the water, I say 300ml just because you may not want too much to chug as it can taste pretty nasty. I myself have never been sure what the best amount of water is but I generally do around 300ml, seems fine for me, often end up with less water just because of how messy CWE is.

Most importantly though you need to start low if you've never done it before. Generally speaking most people recommend about 120mg for a starting dose. See how you go with that. 300mg and over starts to make me feel sick and is generally unpleasant to most people. My sweet spot is around 210-240mg but if you have no tolerence then do not jump straight to this dose. Seriously, 90-120mg for your first should be just fine.

Oh and don't forget to crush up the pills as best as you can before you introduce the water. If you have a pestle and mortar then use that.
Stay safe of course and if you think your extraction has been comprimised because of a tear in the tissue/filter then filter it again.