It is not clear as the copy of the SB being referenced is unformatted; but if memory serves me correctly, as I am no longer working on the BAe 146, the "BAe 146 / Avro RJ" title at the top of the page is just a generic header for the aircraft family of the SB publications.
The actual effectivity is detailed further in the SB and only refers to BAe 146 (and so not Avro RJ). But as other posts have well stated, the clear effectivity can be determined by reading the actual SB itself, and not the summary, against the aircraft serial numbers. Hope this helps.