I'm not reading this clearly so I'll guess what you're saying.
You have a $100M Loan that was paid down to a balance of $50M (outstanding in 2004) at which time you advanced an additional $50M? If this is the case, report $100M. (The balance at the time of the modification and extension).
Or did you pay off the $100M all together and advance another $50M for some goofy reason
(verses doing a new loan). If the total extended credit in 2004 was only $50M, report that amount.
I think I answered that both ways so you should have something to go on