hello, I'll draw a line to calculate the distance:
Notice that excepting the first, all spaces have the measurement of 2 unities, right? The only difference is in the first, which measurement is equal to 1 unit.
So, to we find the distance between 13 and 0, we have to sum the measurement of all the spaces. Let's do it:
1 + 2 + 2 + 2 + 2 + 2 + 2 = 13 unities of space