It appears to be a relatively-complex financial product that uses CGT allowances, combined with ISA-status,to produce the returns that it claims. There is risk associated with every investment product - and this is an investment product, not a savings product as you suggest in your title. In the case of this product the returns will be far less if the FTSE100 index fails to hit to particular series of future thresholds. The figures shown in the bumpf alos assume that the investor is a higher tax-rate payer.
To be it another way, you need proper financial advice before deciding to invest your retirement funds in such a product. Not saying it's a bad idea - you just need to be properly advised.