There are constraints on how quarks combine, according to the standard model, which mean (among other things) that you won't get three of the same quark combining to form a particle. The cc subscript indicates the presences of two charm quarks, and the ++ indicates the particle has an electric charge Q=+2. The subscript values show the presence of heavy quarks: charm (c), bottom (b) or top (t) quarks are heavy. The superscript is electric charge (Q), a value between -1 and +2 (-, 0, +, or ++).