I am trying to wrap my head around Margin Costs when running some options strategies.

I am using the IB equations from here, IB Margin Eqs

As an example I will use the first Z13 trade. See log below. This is using the Put strategy with Leverage of 6.
Code
Sell at prem 1462.00 max win 1462.00
[SPY::SP11102] Place 2 Put 20120218 134.0 200@7.31 Unl 127.50 at 15:40:00
Com 2.00  Mrg 4702  Net 0  Prem 1462
Units 90.0000  MTotal 0.00  MCost 23.5088 PCost 0.90000 Opn 111


Underlying, 127.50
Bid, 7.31
Strike, 134

Index Options
Margin = Put Price + Maximum ((15% * Underlying Price - Out of the Money Amount), (10% * Strike Price))

Margin = 7.31 + Max(0.15*127.50-0, 0.1*134)
Margin = 7.31 + 19.125 = 26.435

So with Multiplier=100 and Lots=2...
Total margin cost is $5287, correct?

Looking at the Z13 log the premium seems correct. 7.31*100*2=1462
However how is the margin only 4702? I see the MCost*100*2=4702 which matches the Mrg value. But I don't understand where this comes from.
What is the last line in the log? I cannot find anything in the manual describing these names.

Code
Units 90.0000  MTotal 0.00  MCost 23.5088 PCost 0.90000 Opn 111

Units 90? PCost 0.9? Opn 111?