So unfortunately I don’t think job bank will help you in making an argument.
There are no minimum income requirements however IRCC can refuse the application if your pay is too low and they therefore don’t believe you are doing a NOC B job.
I don’t know where you found the information quoting $12.35 and $13 as the lowest pay rate for Administrative Assistants. The first one ($12,35) looks either wrong or old since minimum wage in Manitoba is $12.65. However the link that shows the $13 may be helpful to make your argument as long as this is an official government site. So you could provide that link as part of your response. If you are paid a guaranteed bonus annually on top of your hourly pay, then you may want to include evidence of this as well. Good luck.