A.1.2.1. Adjust Input Delay Chain Value
The value 0 means minimum delay. Increasing the delay value increases the physical delay of the delay chain.
After changing the programmable input delay chain value, you must re-compile the FPGA project and check the I/O timing again. It needs several iterations to find the suitable delay value.
Intel recommends that you set the delay value as small as possible. A smaller delay has a smaller delta part in different PVT, making it easier to meet timing in different timing models.