Ann: Capital Raising Presentation, page-47

It's called a dark pool for a reason. That is because you can't see the order book in the dark pool. So the only way to find out whether anyone is sitting there with a bid or an offer in the dark pool is to test it out by putting a real-money bid or an offer into the dark pool to get that information.
So when you see a 20-share trade at 0.0055 that is someone paying 11c to find out whether there is a bid or an offer in the dark pool.

You hit F5 in your Commsec to find out what the bids and offers are on ASX TradeMatch for free as that is public information.
But you can't see the order book on ASX CentrePoint. You need to put a small order into that dark pool to see if anyone is sitting there with an order opposite to your order.

It's a logical strategy. You pay a few cents to obtain valuable information.