hex, and big numbers...

65000 decimal equals FD-E8 in hex...

why?

65000 is a good number because:

http://www.bgp4.as/

A unique AS number (ASN) is allocated to each AS for use in BGP routing. The numbers are assigned by IANA and the Regional Internet Registries (RIR), the same authorities that allocate IP addresses. There are public numbers, which may be used on the Internet and range from 1 to 64511, and private numbers from 64512 to 65535, which can be used within an organization.

0 to 65535 is 65536 total numbers

and 2 to the 16th equals  65536

and 2 to the 15th equals 32768 which is a number dear to your heart...

and so on...  powers of 2 are not the enemy...
back to 65000...

in hex the rightmost place holder is units or 0-9 ABCDEF (10 - 15) comprising a total 16 numbers because hex is a base 16 number system...

to the left of the units place holder is the 16's place holder...

hex AC is 10*16 + 12*1 or 172...

to the left of the 16's place holder is the 16*16 place holder or 256...

and you love 256... you seeing a pattern here?

to the left of the 256 place holder is the 4096 place holder because 16 times 256 is 4096... every consecutive place holder to the left is again multiplied by 16...

so FD-E8 is...

time to break out the calculator:

F times 4096 + D times 256 + E times 16 + 1 times 8

 ta da...

you can applaud if you want to...