Its a regression, it used to work before.
https://gerrit.libreoffice.org/37672
Thanks Aditya.
Aditya Dewan committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=f94b42d9a8de3c0f9269fc94659707e147d04512 tdf#107762 admin-console: memory graph in 'Analytics' tab now working