On Girnar, “5th tonk” means the 5th sacred spot (shikhar/level) on the hill during the climb.

In Jain tradition:

• Girnar is a Siddh Kshetra of Bhagwan Neminath (22nd Tirthankar).
• Different tonks on the hill mark important places of his tapas, keval‑jnan and finally moksha.
• The 5th tonk at the very top is traditionally regarded by Jains as the exact place where Bhagwan Neminath attained moksha (nirvan).
• Because of this, the 5th tonk is considered the most sacred point of Girnar – a siddh‑kshetra within a siddh‑kshetra.

About present situation (in short, Jain viewpoint):

• Today there is a Dattatreya temple and strong Hindu presence at the top.
• Jains believe the original place is Neminath’s moksha‑bhumi and therefore see the 5th tonk as Jain property and Jain tirtha, not a Hindu site.
• Jain saints and organizations emphasize handling this issue only through ahimsa, legal ways, and peaceful dialogue, while continuing to do bhav‑yatra and worship Neminath Bhagwan in their own shrines and footprints (charan) on Girnar.

You can read more about Girnar and Neminath Bhagwan here

and about the 5th tonk issue here