Exactly, that additionally means that FPPS pool (as any other pool) has transactions losses and as you may notice this expenditure item fluctuates all the time. This is why on the site you may see profitability prediction based on current mining stats and last history.
So far this year it's been anything from 1% to 3%
So an FPPS pool gives some of that 1% to 3% back to the miners.
1. UKRPOOL is NOT a PPS pool.
2. You could read about FPPS https://en.bitcoin.it/wiki/Comparison_of_mining_pools : Calculate a standard transaction fee within a certain period and distribute it to miners according to their hash power contributions in the pool. It will increase the miners' earnings by sharing some of the transaction fees.