"Quetiapine fumarate is an oral psychotropic agent indicated for the treatment of schizophrenia, bipolar disorder, and major depressive disorder. According to Symphony Health Solutions, sales of Seroquel XR® were approximately US$1.1 billion for the 12 months ending January 2017 (TRx MBS Dollars)."
1.1 billion for a year makes something like 22 million for a week. This should still be quite good estimate even though exact number might be a bit higher nowadays.
526K/22M would make 2.4%.
I find that quite good because there has only been a few weeks to build the market and we are talking about breaking to an already saturated market here. The percentage will go higher by time.
B.T.W. The most important number you can query is the weekly sales by MNK. It's not most important is the absolut value correct or not. Important thing is the trend it developes.