53 pay weeks

Hi all, I wonder if some one could help me or give me some advice i recieve chil tax cridits and working tax i gave my estimate last year calculated by wekly pay of 52 weeks however i just realised that due to year ending 5th april which is a friday its going to give me 53 pay weeks making me about 300 over my estimate. does anyone know if this will effect me much or have caused a large over payment?

any help would be great cheers all