Your backup will not work when this message is displayed!
Akeeba Backup / Akeeba Solo has detected that your free PHP memory is less than 12Mb. This will cause a backup error as soon as you try to backup your site's files.
There are two factors affecting your free PHP memory:
The memory_limit configuration variable in your php.ini. This should be at least 24Mb on small sites. A value of 64Mb or 128Mb is highly recommended for most sites. If your host only offers 8Mb, ask them to increase that limit to 32Mb or, if they refuse, use a different host. 8Mb was the standard and more than enough circa 2003. These days it's just way too low to do anything useful.
The amount of software running on your site (only applicable to Akeeba Backup). Each enabled plugin, module, template and component on a Joomla! site and every plugin and template on a WordPress site consumes memory. If you already have a rather big memory limit (64Mb or more), please try uninstalling all unused extensions / plugins and consider using less of them on your site as a good design principle. If you have extensions / plugins working on large datasets, e.g. fetching thousand of articles / posts, consider disabling them and/or simplify your site. The more data you load in memory, the slower your site gets and the less memory is available.
Please do not ask for support for backup failures when this error message is displayed. It is not a bug in Akeeba Backup / Akeeba Solo, it is just your site not having enough memory available to PHP to run a backup. It's like trying to load a very memory-intensive application –like a video editor– on a PC with very little RAM. Everything would be slow and, at some point, just crash.