{$count = $category.products_count}
{$is_first_form = $count % 10 == 1 && $count % 100 != 11}
{$is_second_form = in_array($count % 10, [2, 3, 4]) && !in_array($count % 100, [12, 13, 14])}

{if $is_first_form}
    {$category.fields[2].value}
{elseif $is_second_form}
    {$category.fields[3].value}
{else}
    {$category.fields[4].value}
{/if}