Running out of space again in ~fish-shell/nightly-master

Just as in https://answers.launchpad.net/launchpad/+question/680660, I am getting warnings about running out of space:

Subject: [~fish-shell/ubuntu/nightly-master/xenial] fish 3.0.2-1772-g23eb6e9c-1~xenial (Accepted)

Accepted:
 OK: fish_3.0.2-1772-g23eb6e9c.orig.tar.gz
 OK: fish_3.0.2-1772-g23eb6e9c-1~xenial.debian.tar.xz
 OK: fish_3.0.2-1772-g23eb6e9c-1~xenial.dsc
     -> Component: main Section: shells

Upload Warnings:
PPA exceeded 95 % of its size limit (3953.00 of 4096.00 MiB). Ask a question in https://answers.launchpad.net/soyuz/ if you
need more space.

fish (3.0.2-1772-g23eb6e9c-1~xenial) xenial; urgency=medium

  * Snapshot build from 23eb6e9c

I do not really understand why the repository reports the following:

Number of packages:
5 source packages (78.7 MiB)
42 binary packages (3.8 GiB)
Repository size:
3.9 GiB (96.51%) of 4.0 GiB

We are building 7 binary packages (total about ~100 MB each) across four releases with some old packages in a fifth release. That gives 35 binary packages and a total usage of 500 MB. There's four builds in the last six hours (within the deletion cronjob window), but even that still only adds up to 1700 MB, plus say another 300 for source packages... where is the extra 2 gigabytes coming from?