Those are old school saving throw values.
- Death or Poison (D): When targeted by a death ray or exposed to poison.
- Wands (W): When targeted by an effect from a magical wand.
- Paralysis or Petrification (P): When targeted by an effect that paralyses or turns to stone.
- Breath Attacks (B): When targeted by the breath of a dragon (or other monster with a breath attack).
- Spells, Rods, or Staves (S): When targeted by a baneful spell or an effect from a magical rod or staff.
The above is quoting the OSE SRD. https://oldschoolessentials.necroticgnome.com/srd/index.php/Saving_Throws
The other nuns on the sheet have the same saving throws as Sister Clara, being the same class and level.