Think of the bottom graph as the absolute, the basis.

Now, think of the top chart as a pie chart of proportional %'s of that basis, for each age group... but its not a bunch of pie charts, its a line plot, where the height of each point = the size of each pie slice.

So if every line is at 10 on the bottom chart, then every line is at 20% on the top chart, because... 5 categories, each is 10, thus each is 20% of the total.

...

The other reason they may seem not to match to you is that the bottom chart is log scale, not linear scale.

It is

0 1 10 100 1000 10000

Not

0 10 20 30 40

OP likely went with log scale for the bottom chart because if you did this linear scale...

It would basically just be a smushed together rainbow of lines at the bottom that then sudden blows out into green and brown as cancer and heart failure start killing everyone in their 50s/60s onward.

(EDIT: yep, they actually did a linear scale version, and its as I said lol)

....

The top chart though, is %'s.

%'s of all total deaths in that age bracket.

It thus... must be percentages, as... displaying %'s ... on a log scale... would be very weird.

Like... you could do it... I guess?

But I've been doing data analysis and making reports and charts and shit, and reading them, for a decade+, and I don't think I have ever seen anyone plot a proportional % on a log scale.

The death rate is on a logarithmic scale