WordPress 404 Page displaying on a sub directory that has it’s own 404 page

On a subdirectory such as http://website.com/sub/index.html that has it’s own .htaccess is still for some reason showing the 404 page I have for WordPress which is on the directory above this one.

.htaccess for sub dir:

ErrorDocument 404 /404.html

.htaccess for main dir:

RewriteEngine on
RewriteCond %{HTTP_HOST} ^website.net$ [OR]
RewriteCond %{HTTP_HOST} ^www.website.net$
RewriteRule ^foghelper.php$ http://website.net/subdirone/ [R=301,L]
RewriteRule ^foghelper.php$ http://website.net/subdirtwo/ [R=301,L]
# DO NOT REMOVE THIS LINE AND THE LINES ABOVE jNLK5d:REDIRECTID


# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

Links that were in the hta were censored in case your wondering.