Step-by-step
Population was 12.621 when it was measured
Next year it rose by 6%, so add that 6% to 100% and multiply with population measured
12.621 × (100%+6%) = 12.621 × 106% = 13.379,24
Since a man cant be 0,24, we count that as +1
13.379,24 = 13.379 + 1 = 13.380
That was for a year after measurement, now let's calculate for another year
Now, add those 6% to a new population number
13.380 × (100%+6%) = 13.380 × 106% = 14.182,8
since 0,8 isn't a man, instead we add again +1
14.182,8 = 14.182 + 1 = 14.183
now let's do it for another year after last, by adding those 6% to a newest population number
14.183 × (100%+6%) = 14.183 × 106% = 15.033,98
round it again to +1, since 0.98 isn't a man
15.033,98 = 15.033 + 1 = 15.034
that is it, now graph is in the picture.