You are flying the BISBA1Z STAR to CLE followed by the CLE1L RNAV transition to the CAT II/III ILS Y approach to runway 24L. The box shape is the CLE1L transition.
as stated in the post above, this is correct.
Id recommend you get yourself a Navigraph charts subscription to understand IFR approaches and its STARs/Transitions better. It is really worth it