Problem with Autofit column width

Hello. I applied Autofit Colum Width to some columns. After this, if I want to set a default width to all columns, it works only for the columns that were not autofit. How can I set a default column width for all columns after autofit some columns? It's like to disable autofit for those columns but there is no option to do that.

Look at this example. I applied autofit to columns A, B and C. Next I want to set a default width for all columns, I changed my mind about autofitting columns A, B and C. So I apply the default width for all columns option, and now it works only for columns D, E, F, G, H, etc., but it doesn't apply to columns A, B and C anymore.
ex.PNG

Thanks your your help.

Take note of your Default Width, select the entire sheet then use from the menu bar Column Width and input the same value as Default Width.