Second Job in Tier 2

hi i m on tier 2 visa
i just read on https://www.gov.uk/tier-2-general/overview
and in the section of "What you can and can’t do" it says :

""do a second job in the same sector and at the same level as your main job for up to 20 hours per week ""

At the moment i am on job code 3538 work visa, so how would i check the level of the 2nd part time job, if i plan to do it in future.

Please reply.
Thanks.