In Jain cosmology, the 15 kshetra usually means:

• 5 Bharat kshetra
• 5 Airavat kshetra
• 5 Mahavideh kshetra

At present time, the Tirthankar are found only in the Mahavideh kshetras. There are 4 Tirthankars in each Mahavideh kshetra, so the total is:

5 × 4 = 20 Tirthankars

So, across the 15 kshetra, there are 20 Tirthankars at present.