Because this could mean one of two things.
1. Debra, like any good editor, one month ago put her newest acquisition under the "stack" (probably electronic but still going by the same old name) of manuscripts "to read." A month later, she finally finishes off Manuscript X and finds my manuscript, still unread, at the bottom. She thinks, "Hmm, the author--this... Lora Rivera--has been waiting for a while. I'll ask her for more to give me more time." So she asks for the only thing she doesn't have (having already the full manuscript, the author's bio, and a short synopsis): a "more detailed synopsis."
2. Debra, like any good editor, one month ago put her newest acquisition under the "stack," eventually got to my manuscript, read, oh, say, a third of it, and found it quite intriguing and quite complicated. (It is.) So she sends off for a "more detailed synopsis" to see if the thing is at all viable before spending her valuable time reading the rest of the manuscript.
Let's hope for option 2. It's the best.