I had a similar question about Enlarge Person.
"...The target gains a +2 size bonus to Strength, a –2 size penalty to Dexterity (to a minimum of 1)..."
I initially interpreted it as a +2 size bonus that applied to everything Strength related. (Strength 16 has a +3 stat bonus, +2 for this spell for a total of +5) Another perosn interpreted it as a +2 to the actual Strength Stat. (Str 16 would become Str 18 and a +4 stat bonus)
The issue is more muddy with the Dex penalty. if it were a type of 'bonus', like ability bonus, or enhancement bonus...what if your dex was 10...you'd have a +0 bonus from your Dex stat...but it would be decreased by 2 to a minimum of +1...
I ASSUME these are bonuses/penalties directly to the stats themselves and not a stackable bonus like enhancement, etc...
Am I clear on what I'm trying to ask? I don't think I am...but let me know if it's unclear.