If you had 200 units on Aug 31st, sales of 50 units on Sept 15th, and have printed and purged the OE Invoice Audit List (which writes the shipments to IC Transaction History), then a report backdated to Aug 31st (or any date up to Sept 14) should show a qty on hand of 200 units.

It could only do this if the 50 shipments are in IC History due to purging of the OE Audit list report. If that hasn't been done, then the report will show 150 because it sees a current qty on hand of 150 and isn't aware that any transactions have happened after Aug 31st.