35k makes net 12k (not taxed) + 18.4k (at 20% tax rate) = 30.4k net
In the conclusion, everyone gets a "UBI" of 666 per month, which basically doesn't even cover rent (https://www.statista.com/statistics/752203/average-cost-of-r...). If they would follow this German test, it would need to rise to 1100 pounds per month.
So in this scenario, that average full-time employee pays 48% flat tax on income:
35k taxed at 48% = 18.2k net, plus the 8k UBI leaves this average full-time employee at 26.2k. That is 4.2K less than before.
Looking at that graph at the end, I think there is some "creative graph-plotting" going on, unless I'm seriously mistaken in my calculation.
So how can this be the ideal calculation? The graph and conclusion seems to be in complete error. And even then, 8k per year barely seems like a 'basic income'.