Modular Synth Panels

I just finished my Blacet Time Machine with the Stooge panel.  It all
appears to work first time!  I don't understand the regen control,
though.  I expected it to provide feedback for 'multiple' echoes.  It
does this if I turn the mod mix to 'env'.  I'm not sure why that
affects the regen.  With the mod mix to 'int' I get very little
effect with regen until it breaks into oscillation.

Is this how it is supposed to work?  What does the 'env' really do?

Thanks - Dave