When Does 10 Equal 8.68?

Last night, Alex Rodriguez went 4 for 5, with 3 HRs and 10 RBI. Naturally, when I first heard this, I thought "I wonder how many RV he had?" So I did the math:

AB1......1st & 2nd, 2 outs........HR..2.75 RV
AB2 -- 1st, 2 outs....................HR..1.87 RV
AB3 -- Loaded, 2 outs............HR..3.31 RV
AB4 -- 1st & 2d, 1 outs...........1B...1.00 RV
AB5 -- None on, 0 outs..........F8..(0.25) RV

Total Batting RV for the game: 8.68.

FAQ on ERV Scoring: If he drove in 10 runs, why does he get only 8.68 RV? Didn't he generate 10 runs? He only gets 8.68 because ERV Scoring gives credit for some of those runs to the batters who were on base when he hit the home run, because they did some of the work too. I like think that ERV Scoring takes the actual runs scored and chops them into pieces and divides the pieces among the players responsible for their creation. He also lost a bit by making an out in his last at bat.

Also note that he got the highest RV he could for each homer because he hit them with two outs, e.g. if he hits the grand slam with no outs, the RV is only 2.29 (one of the neat things about ERV is that it shows how valuable 2 out, run-scoring hits are).

To put this in a context us Nats fans can understand, Cristian Guzman would have to do this TWICE to get his season RV back to 0.00, whereas if any other regular did this ONCE they would instantly take the lead in RV for the team.