I think you’re asking about the “4th ara” (era/yuga) in Jain cosmology, but there are a few possible meanings and two major traditions (Digambar and Śvetāmbara) that treat durations a bit differently. To give you an exact number of years, I need two clarifications:

• Do you mean the 4th yuga within the current half-cycle (Avasarpini) or within the opposite half-cycle (Utsarpini)?
• Which tradition are you following: Digambar or Śvetāmbara?

If you confirm these, I can provide the precise year-length for the 4th ara in that context (with absolute year figures, not relative terms).