Update M503 MBL G29 report (#16199)

Marlin/src/module/configuration_store.cpp

           for (uint8_t py = 0; py < GRID_MAX_POINTS_Y; py++) {
             for (uint8_t px = 0; px < GRID_MAX_POINTS_X; px++) {
               CONFIG_ECHO_START();
-              SERIAL_ECHOPAIR_P(PSTR("  G29 S3 X"), (int)px + 1, SP_Y_STR, (int)py + 1);
+              SERIAL_ECHOPAIR_P(PSTR("  G29 S3 I"), (int)px, PSTR(" J"), (int)py);
               SERIAL_ECHOLNPAIR_F_P(SP_Z_STR, LINEAR_UNIT(mbl.z_values[px][py]), 5);
             }
           }
+          CONFIG_ECHO_START();
+          SERIAL_ECHOLNPAIR_F_P(PSTR("  G29 S4 Z"), LINEAR_UNIT(mbl.z_offset), 5);
         }
 
       #elif ENABLED(AUTO_BED_LEVELING_UBL)