Usually immigration will take a look at several aspects for your extension application, including salary but also whether your job is considered matching for your education level. As long as your salary is deemed as reasonably matched for your qualifications, it all should be good to go. The application forms will also have a section for your employer to fill out, so I'd take some time to talk with your employer about this too. I got mine extended last year, with success you'll get a two-year extension. Good luck!