When you file your first insider report for a particular security (and registered holder, if applicable), the system will always ask for the opening balance before you can file actual transaction details. This is required in order to enable SEDI to automatically calculate your holdings of that security as of the date of your transaction.
You should enter the total number for the type of security you held as of your opening balance date. (You will have entered this date on your insider profile and it will appear on the opening balance screen as ‘Date of transaction’). If you did not hold that type of security as of the date of your last opening balance, you should enter ‘0’ as your opening balance.