I'm confused as to how the fe80 prefix is 10 bits and not 16.

fe80 IPv6 Link Local prefix is 10 bits?

@michaelsalyers,
The notation you see is standardized so you understand that the significant bits are the 1st 10 bits of 128 bits.
ConvertFE80::
to Binary...
Binary:
*1111.1110.01*00.0000::
What you see is = 16bits but the
/10
means that only thefirst 10 bits
will remain unchanged...(i.e.FE8..
). So the range in HEX is the following:FE80:0000:0000:0000:0000:0000:0000:0000
through
FE8F:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF
note that the first 10 bits remain unchanged as the last 118 bits do. So `FE80/8 has a range of (2^118) addresses = ~33,230,700,000,000,000,000,000,000,000,000,000,000,000
Cordially,
Ronnie Wong
Edutainer, ITProTV*if the post above has answered the question, please mark the topic as solved.
**All "answers" and responses are offered "as is" and my opinion. There is no implied support or guarantee by the ITProTV team. 
Thanks for the thorough explanation