Could someone please explain to me the example in the image below? I thought I had perfectly understood the two mechanisms, but this example makes me doubt about that

enter image description here:

  • 2
    Which one do you not understand? Where are you stuck?
    – D Stanley
    Jan 29, 2020 at 14:33

1 Answer 1


In price/time priority, the buy/sell orders with the highest/lowest price will be first in priority, with the earliest orders breaking any ties. Once the earliest order is completely filled, the next order is filled and so on. The two earliest orders are for 750 and 250, which can be used to completely fill the 1,000 unit order.

In pro-rata priority, all orders with the same highest/lowest price are considered "equal" and partially filled in proportion to their size. So in the example above, there are a total of 2,000 units for sale at the lowest price of 101, and so 50% (1,000/2,000) of each order is used to fulfil the 1,000 unit order.

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