Something appears wrong here.

Here you see Strength buff 6 is +250
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ID:	1747349

Here you see Strength Buff 5 is already giving me +250
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Name:	strengtbuff2.png
Views:	1
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ID:	1747350

Here is Endurance 6 giving +300 which is correct.
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Name:	endbuff1.png
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ID:	1747348