How to calculate time duration for synchronization

How to calculate time duration at instant of CB synchronization for below example?

Example: Sync is in 10 deg at 0.1 Hz frequency difference.

Solution: I have studied the below answer on SIEMENS/7VE63 auto synchronizer relay manual.

Please how it was carried out and how unit conversion was done?

Answer: Tsync = (10 Deg/0.1Hz)x 360 deg
= 280 ms

hence, Tsync = 280ms

Please explain, i am waiting for reply...