At the AGM financial statements should be presented. They should state income from all source (levies will be the biggest by far) and all expenses for the past year. One source of income should be some amount of interest on money held in the OC’s bank account. Something is wrong if this is not stated in the AGM papers.
Usually, there would be some amount proposed to be levied for the sinking fund (usually an amount anticipated for each year of a sinking fund plan) and some other amount proposed to be levied to meet the budgeted expenses of the admin fund. Usual resolutions at the AGM would be to approve the budget and approve the amount to be levied.
What you end up paying will be the admin fund levy plus the sinking fund levy. There is no predetermined split between these because OCs differ in their regular, annual expenses (admin) and their anticipated but infrequent major items (sinking fund).