Deprecated function used in plugin

I installed this plugin on my dev site for testing, and got the following error in my dashboard:

Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead.

Please update this plugin to use current functions.

http://ww.wp.xz.cn/plugins/online-scheduling-and-appointment-booking/