I DON'T KNOW EXATLY WHAT IS MEANING OF RMS VALUE.BUT NORMAL VOLTAGE RATING IS AT 230V,50HZ AC.
(It often goes at 280-290v.But due to stabilizer it controls to 240v)
RMS = Root Means Square.
A sinewave is sampled for voltage levels, the square root of those samples are calculated, then the samples are averaged together, and the result is squared.
If the sinewave is a perfect sine, an approximation of the RMS value can be calculated by multiplying the peak voltage by 0.707107.
If you already have a stablizer, but it's output voltage is incorrect, then it needs adjustment. The manufacturer should be consulted as to how or where you can get it repaired/adjusted properly.