Hi @Sweety ,
I assume you have a gallery and in which there are several dropdowns for each item and a Label to display the max value. If you would like to get the total of all the max value in the gallery, please follow below steps:

1\ Label inside the Gallery set Text to:
Max(Dropdown1.Selected.Value,Dropdown2.Selected.Value,Dropdown3.Selected.Value)
2\ Label outside the Gallery set Text to:
Sum(ForAll(Gallery1.AllItems As A, A.Label2.Text),Value)
Hope this helps.
Best regards,
Community Support Team _ Jeffer Ni
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