Weird Femara dose

Andy99

I am on a very light stimulation and my dosages for IVF #1 last month was as follows: 

CD3 - CD7 = 5mg Letrozole (Femara) per day

CD4, CD6 = 3 ampules Menopur

CD8 = 2 ampules Menopur

I had 9 follicles and they got 6 eggs at ER on CD13 (6 days after last Letrozole) of which 3 were mature, but none of them fertilized.

We jumped right back into IVF #2 this month and my protocol changed to the following:

CD3 - CD10 = 5mg Letrozole per day (increased by 3 days)

Menopur stays the same as previous cycle.

So my question is, what do you think is the goal with the extra 3 days of Letrozole?  More eggs?  Better quality eggs?  And will it push ER back a few days (possibly to CD15/CD16)?  My concern is that I naturally have a shorter cycle of about 26 days and usually ovulate anywhere between CD10 and CD12.  Will this affect anything or does the medication "override" that completely?  As far as I know, they're not giving me anything to stop ovulation.

Am I just over-thinking it?

Any thoughts or advise would be appreciated.