How is unlawful presence calculated and what will be the impacts?

For your purposes, unlawful presence would start 60 days after the date of your project ending. Persons on H-1B visas are given a 60 day grace period when their employment ends before the ending date of their H-1B statuses. I do not believe that staying for 2 to 3 weeks after the job ends would have any effect upon a consular interview for a dependent visa stamping. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.