Well, you only have a 55g tank and you don't have anything setup in it except the CC, so now would be the perfect time to change it out if that's your desire and it won't be too big a job.
You could either bag up your leftover CC and sell it on craigslist, or if you're an avid DIYer you could use it to make your own agrocrete rock sculptures for your tank.
Now allow me to go off on my doddering old man tangent about my own personal experience with CC...
I bought a fully stocked 125g that already had a mix of mainly gravel and CC for a substrate.
It took all day to break it down, move it to my house, set it all back up and get the fish and corals back in.
There's no way I could have completely changed out the substrate without causing a cycle, so I did the next best thing.
Gravel and CC leave pockets and crevices between the particles that trap uneaten food/detrius which your CUC can't reach and so it rots causing problems.
Also, I don't like the looks of it and I wanted to keep some sandsifting gobies as well.
So I took several bags of Caribsea aragonite LS
and dry sand, mixed it in with the CC to fill the gaps, and then built up another two inch layer on top for a clean white sandbed.
It lasted for two years like that without a problem until the wife decided we needed to rearrange the furniture and the tank got moved to the other wall.
That's when I set her down with a spaghetti strainer and several rubbermaid tubs to sift out all the old gravel and CC before I reaquascaped.
Hey, she's the one who wanted the tank moved... not me.