I make sheet cakes mainly and for me, I score the cakes (if I’m scoring or this is the number of servings I say the cake serves; not teeny but nice sized pieces)
9 × 13″ = 24 servings (6 across by 4 width scored/cut)
12 × 18 = 48 pieces (8 across by 6 width scored)
11 × 15″ = 35 servings (7 across by 5 width scored)