I am little doubtful with regard to below points.

The equation I understood is

d1 +d2 + d3+ d4+d5+d6=19

where each 0$\leq$d_{i}$\leq$9 (Actually answer comes when I take each d_{i} in this range)

my query was why not each d_{i }will be in range 1$\leq$d_{i}$\leq$9

because question mentions for positive integers so each digit must be from 1 to 9.