Learn English – What does “biased in your favour” mean in this sentence

I checked several dictionaries and googled and checked previous biased-related questions here including Is it "biased towards" or "biased against"?, Word for being biased "towards the other direction"?, What do you call a person who is regionally biased? (unrelated),

Moreover, subscription-only LDOCE says:

biased (adj.):

1. unfairly preferring one person or group over another:
   Of course I'm biased, but I thought my daughter's paintings were the best.
   racially biased attitudes.

   biased against/towards/in favour of
   news reporting that was heavily biased towards the government

2. more interested in a particular thing than in another:
   biased towards
   The majority of infants are biased towards being social rather than being antisocial.

OED says:

biase (v.): To give a bias or one-sided tendency or direction to; to incline to one side; to influence, affect (often unduly or unfairly).,
biased: Influenced; inclined in some direction; unduly or unfairly influenced; prejudiced.

But I still can't understand the meaning of the following sentence:

I appreciate that you took the time to contact me. You are great in my opinion! But then I am very biased in your favour!

Does the sentence imply that:

a. The person saying this, is somewhat being unrealistically nice at their own expression of the addressee being great (in a negative way);
or

b. Do they mean that they're not great enough to be able to return the favor (in a positive way being keen on the addressee's greatness)?

I also notice that LDOCE uses "favour" rather than favor, which probably indicates that this usage is British only?