This reading is what is being read by S.M.A.R.T. data from the NVMe itself - it is not a PVE metric & as pointed out - its manufacture dependent.
Most S.M.A.R.T data is usually only useful when looking at it in a relative fashion. So in your case - only you know what you have been doing with the drive & its history. When did this "number" reach 100? How long did it take to get there? At what rate etc. ? This may (or may not) give you an idea of what's actually going on with the drive & how critical is a replacement. In my book - if in doubt replace it.