I want to make a map of India with the population in some cities, with symbol size ranging from smallest to largest according to the population value. I used graduated symbol. I have 13 categories of population and I customised the symbolize from 0.8mm to 15 mm. I want to make the size of large population symbol a bit larger than this. But when I change the largest symbol size from 15 to 25 or 35 no change occur in the map symbols. Only the size of symbols in layer panel is changing.
Is there any way to enlarge the symbol?
I am using QGIS version 3.18.1. I am adding the screenshot of how I changed the size of symbol.

apply, the dots (circles) on the map canvas should change. Did you try that? – Babel May 10 '21 at 08:35size / data driven override / assistant, see https://i.stack.imgur.com/syNaN.png and https://i.stack.imgur.com/L0Sw5.png - does this help? If not: can you change the styles at all (color etc.)? If not: check ifLive updatehas not been disabled accidentally: https://gis.stackexchange.com/a/392993/88814 – Babel May 10 '21 at 08:50