I had two related questions, but first let me set the stage:

Got 4 new 841s, and at the same time sold my old 741 to a friend.  Everything been great for both of us for a few weeks, but for a reason(s) neither of us understand, the settings in the controller I sold to him reverted late last week to my old settings.  So you guessed it - I got credited with his machine's work since the old settings obviously had my worker info until he fixed it this morning:

Question #1:  Any easy way to split out the work?   This is more theoretical than practical - I'm just going to buy him lunch to pay him back but I was curious if there was an easy way to do this if the parties have a agreement on hash rate share (ie I am 4.5 machines he is .5).

Question #2:  While computing on my worker, his machine caused my average "Shares" count to double; yet the "Average Share" value fell by half.   Clearly I don't understand these values like I thought.  I would expect all values to change by a percentage value commensurate with the the incremental hash rate.  Could someone explain how those are calculated?

https://imgur.com/gallery/Pfl2g

Thanks!