Where Are Media Sizes Set? (media.media_details.sizes)

Can anyone advise where media.media_details.sizes set?

I’d like to amend sizes, or add another one.

This is an example of the current set:

1536x1536
: 
{file: 'pexels-adrian-frentescu-6467589-1536x1024.jpg', width: 1536, height: 1024, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…rentescu-6467589-scaled.jpg?fit=1536%2C1024&ssl=1'}
2048x2048
: 
{file: 'pexels-adrian-frentescu-6467589-2048x1365.jpg', width: 2048, height: 1365, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…rentescu-6467589-scaled.jpg?fit=2048%2C1365&ssl=1'}
full
: 
{file: 'pexels-adrian-frentescu-6467589-scaled.jpg?fit=2560%2C1707&ssl=1', width: 2560, height: 1707, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…rentescu-6467589-scaled.jpg?fit=2560%2C1707&ssl=1'}
large
: 
{file: 'pexels-adrian-frentescu-6467589-1024x683.jpg', width: 1024, height: 683, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…-frentescu-6467589-scaled.jpg?fit=990%2C660&ssl=1'}
medium
: 
{file: 'pexels-adrian-frentescu-6467589-300x200.jpg', width: 300, height: 200, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…-frentescu-6467589-scaled.jpg?fit=300%2C200&ssl=1'}
medium_large
: 
{file: 'pexels-adrian-frentescu-6467589-768x512.jpg', width: 768, height: 512, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…-frentescu-6467589-scaled.jpg?fit=768%2C512&ssl=1'}
post-page
: 
{file: 'pexels-adrian-frentescu-6467589-990x525.jpg', width: 990, height: 525, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…entescu-6467589-scaled.jpg?resize=990%2C525&ssl=1'}
post-thumb
: 
{file: 'pexels-adrian-frentescu-6467589-225x158.jpg', width: 225, height: 158, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…entescu-6467589-scaled.jpg?resize=225%2C158&ssl=1'}
thumbnail
: 
{file: 'pexels-adrian-frentescu-6467589-150x150.jpg', width: 150, height: 150, mime_type: 'image/jpeg', source_url: 'https://i0.wp.com/djmixoftheweek.com/wp-content/up…entescu-6467589-scaled.jpg?resize=150%2C150&ssl=1'}
tptn_thumbnail
: 
{file: 'pexels-adrian-frentescu-6467589-150x150.jpg', width: 150, height

Hi, I might be wrong but these are defined in Wordpress, and Frontity just fetch it ?