Swaps are settled once a minute. Once a minute the value of your swap grows by the amount of interest at a rate you specified. Accrued interest is then added to the capital lent to investors in the next minute, allowing you to benefit from the power of compound interest.
For example, if you opened a swap for 1 BTC with an interest rate of 100% per year, in the first minute 0.000132% of this amount, or 0.00000132 BTC, will be added to your account. In the next minute, you will earn interest on the sum of 1.00000132 BTC and so on.