Edit the CSS that is included in the first post. It controls the look of the date numbers in the calendar view. If you didn't add the CSS yet, add it to the second (lower) Additional CSS Definitions box under MainCSS. I didn't want to put it inline and people often customize their CSS.
I have them set at 115% with today set at 130% of the normal size. You can increase those values, make them bold, change the font all by editing the two CSS classes.
Code:
#highlight { padding:0px; border:1px solid red; font-weight:bold }
#calendar_today {background-color:transparent;color:red;font-size: 130%;font-style:italic; font-weight:bold;}
.daybox {padding:0px}
#calendar_date {font-size: 115%;font-style:italic;}