Mismatch axial length and myopia

I have myopia of OS -4.5(SPH) -1.5(CYL) OD -5.25(SPH) -1.5(CYL).

I recently measured the axial length and got the result of OS 25.24mm OD 27.55mm. (one measurement with A-scan)

There were no problems with dilated fundus examination and OCT.

I am 24 years old and has never had any eye surgery, including vision correction.

Could it be a measurement error?

Why do you say that it’s a mismatch? Axial length is not an absolute number, you cannot equate x mm axial length to y mm myopia, because there are biological (mechanical) difference between individuals, and even between individual eyes. So you can only say that z mm axial length changes equates to zp diopter of myopia change. Without knowing what your axial length would be with emmetrope eyes you cannot tell if the axial length is “correct” or not.