There is a 500KB file size limit for the Free plan only. This means that you will not be able to upload files bigger than 500KB if you are on the Free plan.

There is also another restriction that is for all plans (paid too) - you cannot upload a file bigger than 2MB via HTTP, this means that you have to use FTP for files bigger than 2MB. If you try to upload a file bigger than 2MB using the File Manager tool on your web hosting control panel it would say "File(s) uploaded successfully" but the file won't be there.
Please use FTP for files bigger than 2MB.