The other answers ignore Dutch rules

Under current Dutch rules, the original amount of your student loan counts. Source. Repaying is a positively bad idea. It doesn't help you at all.

OP is also using the wrong calculation

The "twice study loan" rule of thumb was based on the old study loans which have to be repaid in 15 years. Since the duration has more than doubled, the factor has decreased from 2x to 0.7x (approximately). Even if repaying would help (which it doesn't), your maximum mortgage would only increase by 70% of what you repaid. Even ignoring interest, that's just a plain bad deal.

OP is using the wrong (outdated) calculation.

The "twice study loan" rule of thumb was based on the old study loans which have to be repaid in 15 years. Since the duration has more than doubled, the factor has decreased from 2x to 0.7x (approximately). Even if repaying would help (which it doesn't), your maximum mortgage would only increase by 70% of what you repaid. Even ignoring interest, that's just a plain bad deal.

Source.

Also note that under Dutch rules, partial repayment isn't credited. The repayment is assumed to shorten the duration of the study load, but OP will be constrained by their current income.