What is the amount of Zakat if the sum was 10,000 Saudi Riyals at the beginning of the Hawl (Zakat year), then it became 6,000 after the first Hawl passed, and then it became 8,000 after the following Hawl passed?

The nisab (minimum threshold) for local currencies is the equivalent of 85 grams of gold or 595 grams of silver. If an amount, such as six thousand Saudi Riyals or more, reaches this nisab and a full lunar year passes while it is in one's possession, then zakat becomes obligatory on it. The zakat rate is a quarter of a tenth (2.5%), which would be 150 Riyals for six thousand. If the amount is less than the nisab, then no zakat is due. The same applies to eight thousand Riyals or any other amount.