The noun phrase the big bra sale in the above sign is ambiguous, in that it has two possible interpretations. The intended interpretation is, of course, ‘big sale (of bras)’, where the adjective big modifies the head noun sale. We can represent this as [ big [bra sale] ]. The unintended interpretation is ‘sale of big bras’, which has the noun phrase big bra modifying the head noun sale: schematically, [ [big bra] sale].
The layout artist who did the following poster was evidently aware of the ambiguity, hence the larger font size for big and sale.