You can not enter any balances in AM-C except the budget amounts.  The actual beginning balance entries must be made in GL-B.  There is a Beginning Balance type entry made in GL-B that is your Year End Balance sheet including total retained earnings through the end of the prior year.  Then, if your DBA start-up date is not the beginning of the fiscal year, you also need to make type 1 GJ entries in GL-B for all the YTD amounts for all accounts including income and expense but NOT including this year's earnings.  The Current Earnings balance will be calculated based on the net of the income and expense accounts.  This can be either a single YTD entry or monthly net change entries.