Multicodec question

I am confused why addPrefix in js-multicodec uses the varint:
https://github.com/multiformats/js-multicodec/blob/master/src/index.js#L29

while the did:key spec https://w3c-ccg.github.io/did-method-key/#secp256k1

the code from table.csv + 01 is used:
https://github.com/multiformats/multicodec/blob/master/table.csv


https://gist.github.com/bshambaugh/424715adc61c0928d5366e741d7da652

Code to convert

zQ3shokFTS3brHcDQrn82RUDfCZESWL1ZdCEJwekUDPQiYBme to
e70103874c15c7fda20e539c6e5ba573c139884c351188799f5458b4b41f7924f235cd

-Brent Shambaugh

Code to convert