Is the amount paid in advance deducted from the total price of the device agreed upon in installments, or is it deducted from the original price of the device before calculating the installments?

If the price of the device is 3000 and it is calculated on the basis of deferred payment, then the accelerated payment must be deducted from the original price of the device, and the installments calculated on the remaining amount, so that the accelerated payment has an effect on reducing the price, and acceleration should lead to a decrease.