If i show staying for 1 week on my visa application but instead stay there for 4 weeks

Hy im from Karachi Pakistan from zia ud din university.

Im confused regarding stating my stay in visa application regarding PLAB 2

I intend to stay for 4 weeks only for my Plab 2 in UK but if i show in my cover letter and visa application for 1 week would that still get me a visa?