How many hours do PhD students work as a TA (total)? How many hours do you work as a graduate teaching assistant and what is the breakdown? (This might include actual teaching hours, office hours, grading, tutoring center hours, etc). 

I am in a Statistics PhD program and am receiving support (tuition plus a stipend). My department has assigned me a full 20 hours. I understand that the support is technically for 20 hours of work, but my understanding was that this was rarely assigned in full having talked to friends at other schools and in other departments within my school. Still, I'd like to hear from a wider pool of people.

Here is my assignment:
one recitation, 40 students (1 hour)
grading for recitation (2 hours) 
weekly section meeting (1 hour) 
prep for recitation (1-2 hours) 
office hours (4 hours) 
tutoring center (10 hours) 

The worst part is that I wasn't allowed to choose my own office hours (and why do I need 4 for a one-hour recitation) or the tutoring center hours, which include evening hours. I highly regret choosing this program. The other program that I wanted to go to assigns two recitations (1 hour each) and ONE office hour, plus grading. 

I look forward to hearing your input. Even if you've graduated, if you remember any of your past teaching assignments, I'd appreciate hearing it.
So are you saying you will only be TAing for 10 hours weekly? And you are unhappy about that?

This work load depends on the university. Some schools are notorious for loading graduate students with lots of TA work. Where I went to school, I had to TA for 20 hours full. 

So if you are only required to work for 10 hours (and are getting paid for 20), if I were you, I wouldn't complain about it. -:)