What does "calls unpaid (aggregate)" refer to in the context of share capital disclosure?

The total amount that shareholders owe on their unpaid shares

"Calls unpaid (aggregate)" refers to the total number of shares that have been issued by the company but remain unpaid by shareholders. In some cases, when a company issues shares, it may not require shareholders to pay the full value of the shares upfront. Instead, the company may make a "call" for the unpaid portion of the shares at a later date, requiring shareholders to pay the remaining amount.
For example, if a company issues 1,000 shares to a shareholder but only receives payment for 800 shares initially, the remaining 200 shares that are yet to be paid by the shareholder are referred to as "calls unpaid." This means the shareholder still owes the company the amount equivalent to the value of those 200 unpaid shares.