The position on the day of the switch
What each account was carrying on the day this system became the record. Nothing here is invented: an account with no opening is one nobody has told us about — not one that is at zero.
No accounts registered.
Create the clients, agents or counterparties first. Only then does saying what they were carrying mean anything.
A positive figure means they owe us; negative means we owe them. Same convention as the current account — debit is always in our favour. Each account takes one opening, once.