nope... no need to worry at all
as to the amount of scanned items, nobody knows
... well the bs should scan hundreds of files during the first boots after a new install, and then the number should slightly decrease, that's all I can say. I don't use the behavior shield anyway, as 1st I don't find it very useful, and second it slows down my system. It's mainly needed by Avast to analyse system behaviors... and yeah, it should be able to block stuff (
)... may be rogue AVs... no idea... anyway it's not supposed to block threats like the other shields do but prevent "unexpected system modification" (sic).