Which number is the official number I should pay taxes on?

I just bought an upgraded plan for one year, thinking that it would give me the ‘one tax number for the tax year’ as advertised on the Upgrade page. However, I don’t see anything new from the free plan, just a split into the wallets at the bottom, which I most definitely didn’t need.

Am I to assume that the tax owed is 20% of the net capital gains and losses? If so, it would be great to get my money back for a plan I definitely didn’t need! I was really expecting something more reassuring to tell you the amount you owe, after paying £44 for it.