One unit is equivalent to 2 British pounds (GBP). Since Jackpot Pools' "base currency" is GBP, all transactions take place in the background in GBP. Then customers around the world play in their local, national currencies and based on the respective exchange rate at the time of play, a conversion to GBP takes place, but you do not see that conversion as a player. The basic rule is thus that a unit / unit corresponds to a line with a stake of 2 GBP.
This means that a line with a bet of eg 2 EUR does not really become a whole unit, since it depends on the current value of the British pound against the euro. It also means that a line with a bet of 20 SEK does not really become a whole unit.