In the Graphical
Data Mapping editor, to copy one element from the
input repeating element (array) to an output simple element, use the Move
transform.
Procedure
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Define a Move transform between the input and the output
elements.
The following figure shows the input and output elements connected by a
Move transform:

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Specify the index of the repeating structure that you must copy to the output.
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Click the Move transform
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Switch to the Properties view.
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In the Cardinality properties page, enter a value in the
Input array indices field.
You can configure the Input array indexes section to select specific
instances of the input array. For more information, see Selecting the indexes of input array elements.
For example, enter 3 to copy the third element in the repeating structure
(array).

There is no option to set the cardinality of the output element, because it is a single element.