Interpretation of the rating of a real transformer
From these specs you know:


Maximum apparent power is 15kVA. This means that the product of Voltage and Current must not exceed 15kVA.
The transfer ratio is 10:1, largely independent of input voltage but may vary some with load.
The high voltage side is rated for a maximum of 2300V(RMS)
The low voltage side is rated for a maximum of 230V(RMS)


And when it comes to RMS, the transformer is probably spec'd for sine wave voltages. This means the peak voltage on high side can be no larger than 1.41 × 2300 = 3250V and 325V for the low voltage side.