The big qualifier when assuming a number like ~238 MACE, even with that ~ symbol denoting approximately...the big qualifier is that we're likely talking about a mix of both adjudicated and suspected MACE.

I'm going to speculate that the 238 number is a combination of both confirmed MACE as well as suspected events, with the suspected figure being reduced a bit.  What I'm suggesting is that perhaps they were at 230 confirmed events when they gave that number, and 10 suspected events....and that they allowed for about a 20% fudge factor in case some events don't get confirmed.  

If my increasingly faulty memory serves I recall a recent poster in which the company communicated a couple of options for wrapping up the trial....one was to wait for 250 events to be confirmed, and then ending the trial and continuing adjudication on remaining events still in process which would likely mean the trial would show perhaps something like 260 events or so.

The other option I'm assuming would be to get to a combination of confirmed and unconfirmed events that based on the % of events that move from suspected to confirmed....that would get to the 250 number.  

The first scenario would obviously take longer....while the second might have the potential to see the trial end with under 250 events, if too many suspected events were not ultimately confirmed.

I know I worded that horribly but I think I got my point across.