I can put a bit of input into this.. as I have had to do it a few times.
this is where I am at with it at the moment.
to check sizes head to here. within your Moodle admin pages.
Mine at the moment.
The main reason you need this is if you are developing courses on another machine then wants to use the backup\restore course commands. As in backup from the development moodle machine instance --- restore to the Bitnami Moodle instance.
It has been a frustrating experience for a number of users over the years, as basically it will stop you from loading large backup course files.
There is plenty in moodle forums on this and is easy enough to do within your own Moodle server if you have got admin rights.
Here is a link to how to for when I have done it on the Synology. it is the step by step process. but with that in mind, there is an easier way now by using WinSCP and or bitvise SSH client. (I have to put in a caveat here as right at this moment I can't get either one of those to write to files within the bitnami backend, but will report back how to once I have got it sorted out again)
how to edit to increase file uploads and timeframes
Hope this helps as I know it is a painful experience. My course backups are sitting at around 120megs.. so 40megs doesn't cut it.
One other trick is to only backup sections of your courses and load them into the Bitnami instance.. takes a bit more time but is a way around it