It was one buy order from you saying “I offer to buy 425 Plex for 2,730,000 each”.
It was matched to two offers: One for 60 PLEX (probably an offer that would accept less than 2,730,000 each) and one for 365 PLEX (probably from the order you clicked “buy this” on).
The price listed is the price you were willing to pay.
Brokered markets are a bit different to a shop - people make offers to trade (“Items for ISK” or “ISK for items”) and the system matches them in an optimal way in the background. Takes a little getting used to.
As to where it went - I can’t help you further (I’m a player with no further information than you:- just experience!) - the best bet is to wait on the ticket. If you provided good information then it should be fairly quick for CCP to confirm what happened. That screenshot will be useful for them - they have full logs of all transactions and activities in game so should be able to get to the bottom of this.
Be nice to them though: the people working on your ticket are busy and human.
Sorry I can’t help further.