UICC_RECORD_BUFFER_MAX

#define UICC_RECORD_BUFFER_MAX   ((256 * 2) + 4 + 1)

#include <include/modem/uicc_lwm2m.h>

UICC record max size is 256 bytes. The buffer size needed for the AT response is (256 * 2) + 4 bytes for SW + 1 byte for NUL. Using 516 bytes is adequate to read a full UICC record.