See the original discussion:

https://lists.gnu.org/archive/html/guix-devel/2020-02/msg00303.html

Our users fall into 2 categories:

- Those with a "small" store partition, say 25 GiB.
- Those with a "big" store partition, say 1 TiB.

If we use a relative threshold, users with a big partition will get
a hint all the time.  This may mislead newcomers into thinking that they
should run "guix gc" while they still have 50 GiB of free space.

If we use an absolute threshold, users with a small partition will get a
hint all the time.

In both cases, the hints becomes irrelevant if it's triggered for the
wrong reason.

The fix is to use both thresholds and to check against the lowest one.

Does that make more sense?

Cheers!

-- 
Pierre Neidhardt
https://ambrevar.xyz/