Subscripted::subv
An error occurs because the second and third arguments in Subscripted give overlapping position specifications:
Subscripted[C[1, 2, 3, 4, 5], {2, 3}, {3, 4}]This shows valid subscript and superscript specifications using Subscripted:
Subscripted[C[1, 2, 3, 4, 5], {2, 3}, {4, 5}]