Professor asked for details of letters I need
The professor wants you to help him/her write the letter. You know what the institution needs and the prof doesn't want to have to explore it separately. You have an opportunity to let him/her know just what you would like emphasized in the letter. 

Some professors even ask for a first draft of their letter and may send it out pretty much unchanged. Make sure you include enough to cover the needs of the granting institution and enough to highlight your own work, especially as it is known to this professor.