If a coin upgrades at PCGS, where would they place it at the next grade level.....low end or high en

For example, if I sent in a coin (let's say PCGS AU55) for regrade and PCGS felt the coin was worthy of an upgrade to 58, does that mean that PCGS felt this coin was low end for a 58 or high end? 
Just curious what some of your thoughts are on regarding this matter.
Thanks.

Just curious what some of your thoughts are on regarding this matter.
Thanks.
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Comments
"Don't fall into a trap thinking that the only upgrade that you might get through the Secure Plus line is a +. I have seen several coins that upgraded a full point and even a few that upgrade a full point plus the + !!"
I sent a PM recently to Don Willis asking this exact question (title of thread) and am now waiting for a response.
It sounds like every coin has its own merits and will be judged accordingly, but I'd sure like to get an answer back from Don.