You may have seen the latest offer in game right now called Holiday Coin Offer 1.
You get 2,650 coins for £28.99. It says you get an extra 15% coins.
Alternatively, you can buy the 2,300 coin package and the 330 coin package for £29.27.
The offer only gives you an extra 20 coins with a saving of 28p.
Therefore, you do not get 15% more coins. You get 0.76% more coins with this offer.