Work experience GRADUATE STUDENT

[ElStu]

Hello all,
I'm a graduate student in Canada and have been working as a teaching assistant for two years now. My HR employment document states that employed in variable hour, contract position as a TA in my department. It does say that I've been working for two years. Can I count this as work experience for express entry Federal Skilled Worker program?
Does my employment document need to specify the number of hours? knowing that it does specify the salary rate.

Thanks!