What makes for the differences between the timekeeping of the various clocks? What is the implicit comparison?

According to the poem, for differences between the timekeeping of various clocks the gongs are beaten out at different frequencies each after half-hour in sequence and slightly differ in time.

The implicit comparison means to compare indirectly i.e. each frequency of gongs represents the condition of different country. And range of frequencies is compared with every different situation in different country that’s why poet has taken the word deeper or lighter.