Below threshold parties are allocated seats first
The final allocation of seats is arrived at in a number of steps.
First the "below threshold" parties are allocated seats. In this step all the first-placed candidates from parties polling below the threshold are confirmed as the constituency winner.
In a parliament of 650 seats: if there were 60 below threshold winners, these would be allocated seats first.
The remaining 590 seats would then be divided proportionally between the "above threshold" parties.