Attributes stack and do not stack ! ( jewelery )

[Alitis]

Hello Hearthlings ! ( this is my first post ever so nice to find you all )

I have a question, so I crafted two beast rings with str +7 and agility +3 each.
When I wear them, the first one adds the attributes normally, the second one adds agility ( so stacks to +6 ) but does not stack strength !
please tell me if i do not understand something...

thank you in advance for your answers.

[azrid]

you can buff stats 2x of your base only

[Alitis]

that makes sense... thank you.