You have bought the right, but not the obligation, to sell £10 per point on the FTSE 100 at a price of 6110, rather than the current price of 6135.3.
For this right, you have paid a premium spread of 23.7 points, meaning you will be in the money once the FTSE 100 drops below your break-even level of 6086.3 (6110 – 23.7).
Alternatively, you could choose to ‘sell’ this option at the bid price of 18.4. This would oblige the seller of the put to buy the FTSE 100 at the predetermined price of 6110 should the buyer of the put decide to exercise his option. In this example the break-even level of 6091.6.