yep, that's J6.  I don't know off the top of my head if that's April or May, but a search on CLH6 and CLJ6 would yield the answer.
Jan - F, Feb - G, Mar -H, Apr - J, May - K, Jun - M, Jul -N
Aug - Q, Sep - U, Oct -V, Nov -X, Dec - Z

April crude is about 75 cents higher than march -seasonal factors, etc (Natural gas months are very different depending on time of year, crude are very similar)

is it just me or are those letters completely without meaning?
No, it must be you. I'm pretty sure there's a "g" in February.