Key Derivation - CKDprv & CKDpub
If I understand your question correctly you want to take m/0h public extended key: 

xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw

and derive m/0h/1 public extended key?

These are my values:

version: 0488b21e
depth: 02
fingerprint: 5c1bd648
child: 00000001
data: 03501e454bf00751f24b1b489aa925215d66af2234e3891c3b21a52bedb3cd711c
chain: 2a7857631386ba23dacac34180dd1983734e444fdbf774041578e9b6adb37c19


What is b8b9c580 in your result? //edit: I am guessing it's the checksum.

chain input to HMAC: 47fdacbd0f1097043b78c63c20c34ef4ed9a111d980047ad16282c7ae6236141
data input to HMAC: 035a784662a4a20a65bf6aab9ae98a6c068a81c52e4b032c0fb5400c706cfccc5600000001
Calculated hmac: 4eb9d78157bae7a24115001621c4d91e3a3110e11e143c5259eaa4e55c5ec4bf2a7857631386ba23dacac34180dd1983734e444fdbf774041578e9b6adb37c19
left: 4eb9d78157bae7a24115001621c4d91e3a3110e11e143c5259eaa4e55c5ec4bf
right: 2a7857631386ba23dacac34180dd1983734e444fdbf774041578e9b6adb37c19


Looking at your values, they are correct except the HMAC result. In python you'd do:

I = hmac.new(chain, data, hashlib.sha512).digest()


I used bip32utils python library to present the result, the end result (m/0h/1 xpub) is correct.