Telling time

Henry has just finished a time unit at school and is working on telling time, both on a digital clock and an old-fashioned clock.  So, of course, Cora is fascinated by clocks now as well.  One evening she was staring at Dan's digital clock and asked, "Mom, what does the box on the clock mean?"  Huh?  "What box, sweetie?"  "You know, mom, the box right here," and pointed at a zero on the digital display.  Yep, Cora, I guess that does look like a box, doesn't it? 

Then later in the evening, she says, "Mom, it's seven, dot, dot, one, three.  Is that bedtime?"  I'm puzzled and trying to figure out what the "dot, dot" is when I realize that on a digital display, it looks like 7:13 and she was absolutely correct to call them dots, because they are.  Way to go, sweetie !!