how is hex key generated in hbase

[#1]

for a value of 99 , the hbase shows the key value as "\x80\x00\x00c" and for value of 1 in phoenix hbase shows it as "\x80\x00\x00\x01"

how are these values generated? hex of dec 1 is 1 but what is "\x80"? also hex for dec 99 is 63 so how we get "\x00c" ?