Also, there is a reason they are throwing out percentages, instead of numbers. If you read further the numbers are so low you see how absurd all the fear mongering over the alt-right really is. That 150% increase you are talking about is an increase up to 20 total deaths. Even by their loose definition of alt right, more people were probably killed by lightning than by the alt right in 2017.
Of course by mislabeling this as an alt-right killing the ADL is off to a good start for this year in showing how deadly the alt-right is. I mean, if some Muslim guy with mental health issues who may have done some jihadist training at some point or read some ISIS shit on the internet snapped and started shooting up his own mosque with no apparent political motive would it be considered Islamic terrorism? Serious question, because that pretty much is the justification for calling this alt-right.