They say the targets of these attacks were: "Government buildings and officials, individuals, clinics, religious institutions, antiabortion activists, financial institutions, schools, retail establishments, office buildings, media, nightclub."
They cite the source as "press reports" but I would be curious to see what a NEXIS search came up with for that year. My guess is that they are including threats and hoaxes in with their data. Based on their figures, the average number of people affected by each attack was 149.4 and the average number of people requiring some type of attention was 23.5 , so at least one attack had to affect 150 people and require that 35 receive some type of medical treatment. Considering that this is an average number, it is more likely that at least one outlier must have occurred affecting hundreds. I would have thought that this would be a major news story at the time. If it was, I would be interested in reading about it, or at least some specifics.
The article does reference two incidents, one where Larry Wayne Harris made some threats and was found in possession of anthrax vaccine - not anthrax, and the other is where the group named CSA had obtained a drum of cyanide and had plans to poison a city's water supply. Their plan was thwarted when their group was infiltrated by the FBI.
The rest of the article appears to be pure pontification about who likely biological terrorists might be. Considering that the actual source of the article (while written by someone from CFR) is the Center for Disease Control, I would consider it to be much like their gun control studies - fiction at best, but mostly propoganda.