Hey @nestor,
This is unfortunately caused by CSS from your theme, so we can’t offer complete support here. However, you can get started by adding CSS like the following to the bottom of your theme’s style.css file to make the calendar widget width a bit more reasonable:
.tribe-mini-calendar tr td {
padding: 9px 0 !important;
}
.tribe-mini-calendar tr th {
padding: 9px 0 !important;
}
You can play around with those values to adjust the sizing as needed. Beyond this, you should contact your theme developer for more support here, or install a [free!] tool like Firebug if you use FireFox, or the Developer Tools for either Safari or Chrome so you can use the “Inspector” tools of these to find the CSS and HTML you’ll need to tweak to get things looking just right 🙂
Cheers,
George