loading font weights

Hi guys!

I’ve loaded roboto into my child theme by adding this code to functions.php:
$fonts[‘Roboto’] = ‘Roboto:200,300,400,700,400italic,700italic’;

and it worked fine, though i somehow can’t access the font-weight: 300.
Just 200, 400 and 700 – if I set it 300 it has the same weight as 200 – any idea why that is?

thanks!