Let's do some math:
Each BC's volume is selling, at minimum, 2,5K per week since October, and we are in February.
2.5X4 (number of weeks in a month) = 10K
10KX5 (number of months until now, October, November, December, January, February) = 50K
If the growing stay like that and considering it will stop when the anime ends (in October too), we can do:
50Kx8 (March, April, May, June, July, August, September, October) = 400K of boost each volume.
And again, that's just physical sales. That's pretty good to me.