Nope, it's not worked out on 'average', it's just worked out by...

Nope, it's not worked out on 'average', it's just worked out by the overlapping prices/qty and the particular price-point they overlap.

Imagine the BID (buy) prices at the close of the auction are:

0.096 1M shares
0.095 1M shares
0.092 1M shares

If the OFFER (sale) looked like this:

0.066 40k shares
0.095 500k shares
0.097 1M shares

Then at close it's only 540k shares whose price overlaps with the BID side and they would be sold to those offering to pay up to 0.096, so the closing price would be 0.096. The person who was willing to sell for 0.066 would actually get 0.096 per share as all overlapping prices at the end of the auction trade at the end of auction price. The remaining 0.096, 0.095 and 0.092 BID orders and the 0.097 OFFER order would stay on the table as they didn't 'overlap' share-to-share.

If the OFFER was 2,000,000 shares at 0.092 the closing price would be still be 0.095 as there are sufficient buyers at 0.095 for all of these. But if the OFFER was 2,000,001 shares at 0.092 then the closing price would be 0.092 as the 1 x share extra would be enough to push the closing price down to next line on the BID list, which is 0.092. Note this isn't an 'average' it's just the next price down the BID list.

Hope that makes sense, it's good stuff to know