It has 128MiB flash out of which 15.90 MiB available
Also it has 256MiB RAM but /tmp is only 122.34 MiB ?
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 13.0M 13.0M 0 100% /rom
tmpfs 122.3M 292.0K 122.1M 0% /tmp
/dev/ubi0_1 15.9M 6.2M 8.8M 41% /overlay
overlayfs:/overlay 15.9M 6.2M 8.8M 41% /
tmpfs 512.0K 0 512.0K 0% /dev
/dev/sda1 7.3G 24.0K 6.9G 0% /mnt/sda1
root@OpenWrt:~# cat /proc/mtd
dev: size erasesize name
mtd0: 00080000 00020000 "Bootloader"
mtd1: 00080000 00020000 "config"
mtd2: 00040000 00020000 "factory"
mtd3: 00040000 00020000 "config2"
mtd4: 02800000 00020000 "firmware"
mtd5: 00400000 00020000 "kernel"
mtd6: 02400000 00020000 "ubi"
mtd7: 02000000 00020000 "private"
mtd8: 02800000 00020000 "firmware2"
mtd9: 00600000 00020000 "mydlink"
mtd10: 00880000 00020000 "reserved"