Ann: Magellan Global Fund Partnership Offer Opens, page-5

I think the reason MGF has fallen is if you are strapped for cash you sell your current MGF (equal to the entitlement) and then buy the entitlement to get the bonus 7.5% and bonus options.

In regards to "trapped" the total amount of units is fixed and market cap (assume price doesn't move for the example) by adding more units you are increasing both the units on issue and the market cap. In regards to MFG it's FUM increases going forward. From then on you are only able to sell the MGF units on the ASX instead of going and redeeming with Magellan (funds leaving their FUM totals, inflow and outflow).

The difference for the unit prices is simply just preserving their old values (can't have something worth $1 in FUM instantly become $2 only by changing the code).

So a combination of the three is happening at once, all my opinion of course.