IGF : How localized?

[musqlar]

is it localized such that if I want rear delt development I need to inject in the rear, not the medial delt?

Or is it even more precise such that I may want more development in the lower area of my biceps I pin it in that specific spot?

Or is it only generalized such that I can pin the bicep and the tricep will get some bleed over benefits from it?

thanks,