Ideally, for my OVP feature to work, I need to keep the resistor
divider such that the OVP threshold value is more than 9V, right? But
according to the electrical characteristics table, the maximum value
of OVP is 6.3V.
The OVP threshold is typically 5.6 volts and might be as high as 6.3 volts or, as low as 5.25 volts. So, to prevent the normally expected 9 volt output tripping the OVP (a safety mechanism to protect the output and load), you need to ensure that the resistive divider from the 9 volt output to the OVP input is just below 5.25 volts: -
So, if the output rose to (say) 9.05 volts, the OVP would trip. However, because you cannot be sure of the OVP threshold, the output might have to rise to 10.8 volts. So, you have to decide whether 10.8 volts on the output is too much and, if it is, you'll have to use select-on-test resistors in the resistive divider to ensure the OVP trip comes in at slightly above 9.0 volts. From the data sheet: -