Apply Light version of a font when multiple files are uploaded - mpdf

Question

I am having an issue with applying a Light version of my font, when declaring a custom local font.
This is how I declared it:
$mpdf = new \Mpdf\Mpdf([
'fontDir' => array_merge($fontDirs, [
drupal_get_path('theme', 'my_subtheme') . '/fonts/',
]),
'fontdata' => $fontData + [
'proxima' => [
'R' => 'ProximaNovaRegular.ttf',
],
'proxima light' => [
'R' => 'ProximaNovaLight.ttf',
],
'proxima bold' => [
'R' => 'ProximaNovaBold.ttf',
]
],
'default_font' => 'proxima'
]);
But whenever I write 'proxima light' in my css the font remains regular.
I also tried with this snippet:
$mpdf = new \Mpdf\Mpdf([
'fontDir' => array_merge($fontDirs, [
drupal_get_path('theme', 'my_subtheme') . '/fonts/',
]),
'fontdata' => $fontData + [
'proxima' => [
'R' => 'ProximaNovaRegular.ttf',
'B' => 'ProximaNovaBold.ttf',
'L' => 'ProximaNovaLight.ttf',
]
],
'default_font' => 'proxima'
]);
But I don't know how to call it and I didn't find a working example on the internet.
If I only declare my Light file, then it makes everything light.
$mpdf = new \Mpdf\Mpdf([
'fontDir' => array_merge($fontDirs, [
drupal_get_path('theme', 'my_subtheme') . '/fonts/',
]),
'fontdata' => $fontData + [
'proxima' => [
'R' => 'ProximaNovaLight.ttf',
]
],
'default_font' => 'proxima'
]);
I really don't know how to continue from here, am I declaring it wrong? The problem is I need all 3 versions of the font.