The remaining stones do not hold carvings of umbrellas. What he will find if he looks at all of the stones:

a set of short vertical lines both thick and thin — 5 hash marks
a flower shape with long thin petals — 12 hash marks
a five-pointed star inside a circle — 3 hash marks
a small bird — 4 hash marks
a cross shape with even length arms and three prongs at the end of each — 10 hash marks