Perhaps something like the code below (change the ID)…
Note: you can target it using a Field Key or custom CSS ID
<?php
/* START: Changes height of Gallery Field */
function my_change_gallery_field_height() {
?>
<style type="text/css">
#acf-field_59aefd2fd922c {
height: 210px;
}
</style>
<?php
}
add_action('acf/input/admin_head', 'my_change_gallery_field_height');
/* END: Changes height of Gallery Field */
?>
Let me know if that does it for you, and kindly mark as resolved if so!
