When you initially set up a monthly or auto-renew, capped IO both the IO total and your remaining amounts are equal. In case you add an additional IO, your remaining budget will increase. However, your total budget will remain the same as it indicates the total amount of the monthly recurring capped IO.
i.e. when you initially set up an auto-renew or monthly, capped IO of £500,000 your budget total will be £500,000, whilst your remaining amount will start decreasing based on your campaign activity as seen in figure 1 below:
If however, you choose to add £60,000 more to your existing capped IO before its end date, your available budget will increase leaving the IO’s total recurring budget unchanged. Figure 2 shows changes to your monthly recurring IO after adding an additional £60,000.