change size font of mx modules is impossible

i changed element of my homepage with TD-composer
i’ve choosed ‘Big Grid 3’ (module : mx5 + mx6 + mx11)
but the size font is too big especially with ‘module mx5’

so i went to ‘Theme Panel’ of Newspaper / ‘theme fonts’ / ‘module mx & other – article title’ :
to change the size font of ‘module mx5’ to the minimum (size 5px)

i save but nothing change
i do the same change with ‘module mx6’ and ‘mx11’ = nothing change
and nothing change too, with parent or child theme

any idea what i do wrong or miss, please ?

WP 4.9.1
Newspaper 8.7.2