Hello Cathy H,
Thank you for your question on changing the widget size in the footer. The widgets are set to take a percentage of the footer based on the number of widgets selected. If you have three widgets, they each take up 33% of the footer. With four widgets, they each take up 25% of the footer. This also scales with the resolution of the screen as it is shrunken or stretched. If you hard set the widths, you destroy the ability for each visitor to see the footer scaled according to the rest of the page.
Kindest Regards,
Scott M