Thanks for your remark and cross-checking the numbers! A '1' got lost there: 28.7 -> 28.17.
The 28.17% are all votes directly from the bid-bots and paid voting services. On top of that are 3.82% + 1.44% from the vote sellers via smartsteem and minnowbooster.
In total 33.43% for bots + vote sellers for that specific day.