It depends on the individual Deer Knight, its parents (if it was a hatch), and what selfish talents are manifested in the pet as selfish talents do nothing except raise stats. For example, a first generation Deer Knight has Canny in its pool; the DK's Will stat will increase by 40 when Canny manifests. (That extra 40 in the Will stat won't count when figuring the Will stat in any offspring you produce by hatching the example first generation Deer Knight with Canny manifested, however.)
Sorry if this is vague and confusing. This is the most concise way I could think of to answer your question.
Miranda Nightsinger, Promethean Necromancer Scarlet Windhammer, Magus Pyromancer