Repository size is estimated/shown wrong

Summary

Repository size is estimated wrong and it prevent push to it.

Steps to reproduce

git clone git@gitlab.com:eyeo/adblockplus/chromium.git adblockchromium
du -sh adblockchromium/.git

Example Project

git@gitlab.com:eyeo/adblockplus/chromium.git

What is the current bug behavior?

At gitlab.com repository page it's shown to be 17.7 Gb. It's measured wrong and it prevents pushes (prepush hook).

What is the expected correct behavior?

It's shown to be 8.6Gb large and allow pushes.

Relevant logs and/or screenshots

Снимок_экрана_2018-07-13_в_16.53.26

~/adblockchromium68.space anton$git clone git@gitlab.com:eyeo/adblockplus/chromium.git adblockchromium.space
Cloning into 'adblockchromium.space'...
remote: Counting objects: 10509648, done.
remote: Compressing objects: 100% (1640036/1640036), done.
Receiving objects: 100% (10509648/10509648), 8.19 GiB | 2.44 MiB/s, done.
remote: Total 10509648 (delta 8269968), reused 10489148 (delta 8249582)
Resolving deltas: 100% (8269968/8269968), done.
Checking out files: 100% (286238/286238), done.
~/adblockchromium68.space anton$du -hs ./adblockchromium.space/.git
8,6G	./adblockchromium.space/.git

Output of checks

This bug happens on GitLab.com

Possible fixes

git gc ?