Timing the follicular size and IUI.

Hello we are planning for IuI this month . Doctor prescribed letrozole 2.5 mg which was started on day 2-5 of period . Scan on day 8 suggested 2 dominant follicles on left ovary size 17.9x14 mm and 10x9 mm and one on right ovary 8x7 mm. ET lining is 8.9 mm We checked with scan today which is day 10 where one follicle in left which is 15x14 mm and one follicle on right was observed with endometrial lining of 8.4mm. The size of follicle reduced from day 8 to day 10 and doctor suggested it can be observational error and told to take it as 16 mm as average . Suggested to take FSH injection today and tomorrow and asked to review the scan again on Friday evenings or Saturday morning to check for follicle size. Which day is better to do the scan ? And what if the follicle ruptured on Friday and IUI is done on Saturday . Will timing impact the IUi if follicle is already ruptured on Friday and we do the IUi on Saturday? Will egg stay for a day before it degenerates. Kindly suggest .