Great 4th qtr results, only wish oil price had stayed higher a...

Great 4th qtr results, only wish oil price had stayed higher a little longer.

i have a question re the debt position, STO mentioned back in Sept they had achieved the target of $2b net debt, and the acquisition of Quadrant would require $1.2b in facilities therefore one would expect net debt to be $3.2b...
The 4th qtr report is showing net debt at $3.6B theres a difference of $400m is that something of a concern or are they putting those funds aside to pay a bigger divvy? (capex came in under forecast so that side of the ledger didn't chew it up?)

eg, total debt in sept qtr $3.8B + cash eq $1.8B = $5.6B
add new facilities $1.2b = $6.8B
less quad cost $2.15B = $4.65B

4th qtr report shows total debt $4.9B (not to mention higher earnings rec'd for qtr and quad costs less adjustments etc) 

What am i missing??

rc888