RL78/G13 - RTC Clock frequency is reduced when changing the oscillator clock to subsystem from main clock.

Hi,

We were using internal RTC interrupt to wake up from StandBy mode. We required a low-power device, to achieve this we changed the oscillator clock from MAIN CLOCK to SUBSYSTEM CLOCK and then switched to HALT State.

But What we observed is that RTC ALARM Interrupt generation time increased to 2 twice of average time consumed.   

[ Example In Main Clock Alarm generated for every 1min means it take 2min to generate Alarm in Subsystem clock.

We are using Renesas rl78/g13 MCU, e2 studio, and CC-RL compiler. 
Version - v1.11.00