css to remove borders in popup

Hi,

I’m trying to remove the borders from the popup but, scratch my head, I can’t seem to change this css which is reported to be in line 40 of this file:
…/wp-content/plugins/spiffy-calendar/styles/default.css?ver=1500495032
which is a different file then this which I have saved via ftp:
…/wp-content/plugins/spiffy-calendar/styles/default.css
the reason I want to remove the border is that it would look minimally ok if they were gone because I can’t seem to be able to edit the padding in the popup.

Thanks for advise