Font thickness problem

Hello! I try use font thickness for body Open Sans font. In theme options I select Light thicknes for tag “p”. Then add this in Child function.php

add_filter( 'avf_google_content_font',  'avia_add_content_font');
function avia_add_content_font($fonts)
{
    $fonts['Open Sans'] = 'Open Sans:300,400,600';
    return $fonts;
}

But in result not included thicknes 300 Result string -> <link rel=’stylesheet’ id=’avia-google-webfont’ href=’//fonts.googleapis.com/css?family=Tenor+Sans%7COpen+Sans:400,600’ type=’text/css’ media=’all’/>
How to add thickness 300?