URGENT: Trying to revert to original firmware, but Failed to erase block

Could you please explain how I calculate the: dd skip=(strip header) from this:

root@MacBookPro:/mnt/d/.wsl# binwalk Archer_C50v3_EU_0.9.1_0.5_up_boot\[170822-rel64885\].bin

DECIMAL HEXADECIMAL DESCRIPTION

--------------------------------------------------------------------------------

82288 0x14170 U-Boot version string, "U-Boot 1.1.3 (Aug 18 2017 - 09:57:27)"

132096 0x20400 LZMA compressed data, properties: 0x5D, dictionary size: 8388608 bytes, uncompressed size: 3650664 bytes

1442304 0x160200 Squashfs filesystem, little endian, version 4.0, compression:xz, size: 5239848 bytes, 692 inodes, blocksize: 131072 bytes, created: 2017-08-22 10:01:28

Thank you