USB Device Layer Advanced String Descriptor Table Entry Format Enable. 

Specifyin this macro enables the Advanced String Descriptor Table Entry Format. The advanced format allows the application to specify the String Index and the language in the entry itself. In the basic format, this information is obtained by the virtue of the entry index of the String Descriptor in the String Descriptor Table. Using the Advanced format allows the application to specify strings with arbitrary strings indexes. In basic format, the string indexes are forced to be contiguous.

#define USB_DEVICE_STRING_DESCRIPTOR_TABLE_ADVANCED_ENABLE 

The basic string descriptor entry format is selected by default. The advanced format must be enabled explicitly by specifying this macro.