For each “Frequency mode” listed in the DLL frequency range specifications table in the device datasheet, certain “Number of Delay Chains” are available in the device DLL. Dividing 360 degrees by the “Number of Delay Chains” available in each frequency mode will give the “Available Phase Shift“ for that frequency mode.
For example in Stratix® IV devices, when “Frequency mode” is zero, the corresponding “Number of Delay Chains” is 16. Dividing 360 by 16 will give the base “Available Phase Shift” of 22.5 degrees. For the Available Phase Shift values for the device you are targeting, refer to the respective device handbook.