Yeah, delete those rogue admin users if they are not users that you added.
Also, the Complete Scan should not be going that slow. On a decent server you should be able to scan 400 folders in about 4 minutes (100 folders per minute), and on a slow server you should still get those 400 folder done in no more than 8 minutes (50 FPM). Your server looks to be scanning only around 23 FPM, which is extremely slow even for a bad server, so something else must be wrong which is making it take so long. Also, 10,000 folders is a lot for one site, is it possible that you have other websites installed into sub-directories within the root folder of this main website?
Can you send me a screenshot of your scan settings and maybe check your error_log files to see if there are any PHP errors that might be causing the scan to run so slow?