W4 Form making changes if i only worked 2 jobs for a total of 10 days

I recently started a new job on 12/1 and I put my resignation notice to employer. During the time of 12/1-12/14 I was working both jobs. Currently, as of 12/15 i am only working one job. How would not making a change on my previous employer and when filling out new employer W4 affect amount of tax refund or owing money?

 

What can I do ?