"Unpacking objects" question

Hi,

Recently I stumbled upon git unpack-objects documentation, which says:

Read a packed archive (.pack) from the standard input, expanding the objects contained within and writing them into the repository in "loose" (one object per file) format.

However, I have some questions:

1. When I do git fetch, what is the threshold/limit for "Unpacking objects",
    in other words what is the minimum number of objects for invoking
    "Resolving deltas" instead of "Unpacking objects"?
2. Can the threshold between unpacking objects and resolving deltas be
    configurable?
3. Why in some cases Git do unpacking objects where resolving deltas
    can be done?

Thanks.

-- 
An old man doll... just what I always wanted! - Clara