Ah yes, you're right. I read it as "% ot total population of that specific age group" and I guess that is what is meant, but it is not very well phrased indeed.

Percentage of total for each generation. Your assumption of this info is that we should add them together. But if you look at the opposite numbers (percentage of those not identifying as LGBT+) you get 97% + 96% + 93% + 84% + 72% giving us a grand total of 442%.

Obviously you can't have more than 100% of anything but it does illustrate that addition is not the method we should be using.

Instead we average them. Giving us 11.6% of the total population identifying as LGBT+.

The real information we're seeing is that the amount of those who identify as LGBT+ increase with every generation.

"More than one in five young Americans (18-29 years) identify as LGBTQ (22%). One in ten people ages 30-49 (10%), 6% of people between 50 and 64 years, and 3% of people 65 years or older identify as LGBTQ. Twenty-four percent of Gen Z Americans (aged 18 to 25) identify as LGBTQ."

Strangely percentages are a bit off though.

https://www.prri.org/research/views-on-lgbtq-rights-in-all-50-states/

Numbers pulled out of my arse for illustration

Say of the whole population GenZ is 25% and GenY is also 25% (for convenience). If then 28% of GenZ identify as LGBTQ+ that would be 28%*.25= 7% (25% of 28%, or 1/4 of 28%). For GenZ maths would be 16%*0.25=4%. So these two groups would in total contribute that 11% of the total population is LGBTQ+.

Hopefully that makes sense.