If numerical reasoning is clearly the weaker section, it makes sense to allocate more time there, but not 100% of your preparation. You still want enough exposure to the other modules that the format does not surprise you.

A 70/30 type split can be reasonable if the diagnostic gap is large. Recheck the balance after a few sessions because the weak section may improve faster than expected.

Use performance data to allocate prep rather than an arbitrary fixed percentage. Move time toward the section creating the biggest score risk. If useful, this guide on Bain TestGorilla guide gives more detail.