Pause and Think

Why is it that we pause for so long after giving someone the first section of a multi-digit number?

I was never annoyed by this until I worked as a hostess for three years. if a party of 5 or more made a reservation we were required to get a phone number, and it went the same way every time:
"Alight, and can I get a phone number with that?"
"Yeah, it's 536 ... ... (wait for more seconds)... 2159."

Ok. Thanks for giving me seven seconds to type in 3 numbers, that's always really hard for me. 

I like to think I've pretty much stopped doing this when I recite my phone number, but I have found that the habit has yet to die in other areas of my life.

Earlier, for example, I went to talk to an advisement counselor about career options within my major. My name wasn't on the printed list, so she asked for my student number in order to look me up.

"Yeah it's 32........5616079."

What?? Why did I give her like half a minute for the first two numbers and then run the last seven into one word?

Do you ever catch yourself doing this?