Is it a bug or am I doing something wrong?
Settings for file size set to 17 megs and tried uploading an MP4 12.2 megs
AI-generated summary
A user (hipp0) is unable to upload a 12.2 MB MP4 file despite setting the maximum upload size to 17 MB, questioning whether it’s a bug or user error. Moin asks how the setting was changed and suggests following the official guide at Change the Maximum Attachment Upload Size. hipp0 confirms they adjusted it via settings and asks if uploads can be restricted to subscribers only. Canapin replies that this isn’t currently possible, linking to two relevant topics: Limit File Uploads by Trust Level and Restrict File Upload to Group or Badge. They also advise searching for existing answers and caution that restricting uploads may lead to broken external image links, citing a past incident on their own forum. Moin suggests using the theme component Restrict Uploads, which blocks uploads for lower trust levels, and notes it could potentially be modified to support group-based restrictions instead.
How did you change it? Did you follow the steps in Change the maximum attachment/upload size
Okay I just did it in settings.
Is it possible to change uploads to only allow subscribers?
There are two topics about this and it’s not possible.
If you haven’t already, I suggest you do a quick search when you look for basic information, they might have already been answered in the past 
Jay has a point tho:
Allowing some users to upload files while others cannot may inconvenience both users and admins. External links are unreliable by nature, likely to expire in the future, or worse, be automatically replaced with something else. That has happened on one of my forums.
There is a theme component Restrict uploads which blocks uploads for lower trust levels. Maybe you can extend that to be group-based instead of trust level based.