Licensing Question Regarding Chief Engineer Limited Endorsement

I just recently got hired at a tug and towing company as an engineer on a harbor tug. The crew, including the Captain, have all referred to me as “Chief.” I was wondering why they were, then did some research and found that since I’m the only engineer onboard, I’m technically the “Chief” Engineer. Researching even further, I found a flow chart on the USCG NMC website that lays out how much time and certain tests which require an upgrade for your license. There was a part in there that confused me. As far as I have come to undertand, I require only 360 days worth of sea time to upgrade to my 2 A/E license. With that being said, on the flow chart there was a dotted line connecting the 2 A/E slot with the C/E Limited slot. Does this mean that after 360 days, I’m technically both? or is there another test/few hundred dollars I need to give in order to receive that upgrade?

also, is there any benefit pay wise to be a C/E limited opposed to just a 3 A/E working on smaller vessels around the 4,000 - 5,000 HP level?

Thanks guys!