I need advice asap on a gpa situation!

[NeedsAdvice]

I will start by saying that i did use the search function and could not find anything that pertained to my specific problem so please don't tell me to try that. I have been reading the great advice on GC all summer for my upcoming recruitment. I am a Junior transfer at my school and in high school had a 3.7 gpa. I know that high school gpa doesn't matter anymore i'm just putting it out there to show that I am a good student.
I signed up for recruitment and then was notified that my 2.79 transfer gpa was flagged in the "gray area" for gpas and i'm not sure what "gray area" means in this case. I know that my school has 2.5 gpa requirement for recruitment and I thought my 2.79 meant that I was in the clear for grades. They said we can write a letter to explain the situation for our low gpa and i'm really not sure what to do. I was caught off guard about this information and am very confused. I don't feel that a b/b- average is a horrible gpa and of course they are letting other girls rush with as low as 2.5. My last two gpas were a 3.8 and 3.2 but I have a lower from my freshman year that is bringing my overall down. I know that I am a good student and I am slowly but surely raising my gpa.
I know that my junior status already is a strike against me and now with this I feel like I am going to be dropped after the first night! I do have a somewhat decent explanation for the one semester gpa that is bringing down my overall gpa but i need some advice from you gcer's! Why am I in this gray area? How long should my letter be? I am just really nervous and confused now. I feel really unconfident about recruitment because it seems everything is working against me.