Robert and Cora celebrate their 34th wedding anniversary meaning they got married in 1890. However in the first episode set in 1912 Violet says that they had been married for 24 years.
The brunch scene in which the Dowager's butler, Spratt, snubs Dr. Clarkson was added for comedy, but would have been grossly out of character for any servant. Dr. Clarkson was a highly respected member of the village and held in higher esteem than Pratt, who could not have expected that he would only wait on nobles. In addition, Dr. Clarkson was an invited guest of the Dowager, who would not have been amused in the slightest if any of her servants had been rude to any of her guests.