Will a shelf that comes with its own anchors hold up more weight than it says it holds hold up more weight if I add anchors?

Like it says it holds 20 lbs and it’s about 2.5 inches thick but it’s like hollow.. but each one of the brackets say it holds 80 lbs each..
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I feel like for $35 a shelf 36 x 6 should be more heavier
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+1 y
Not anchors! But brackets
Will a shelf that comes with its own anchors hold up more weight than it says it holds hold up more weight if I add anchors?
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