. . . . . as a primer, I am not posting these to mock the people making the mistakes, I make enough myself to last a lifetime . . . . .
as shown in the market window for this Eifyr implant the sell orders are mostly around the 1,288,997 mark and there is a buy order at 260,000.03 ISK.
However, there is a sell order at 260,000.04 ISK. Clearly, this "seller" meant to post the order as a buy order, and the best buy order at that. However, they blundered and posted as a sell instead - which is not hard to do if you are in a hurry.
Alternatively, they meant to sell a sell order that was posted at 260,000.04 which maybe had 3 item at that price and the seller put on a sell order for 8 items at 260,000.04 but of course only 3 were filled leaving 5 to go.