Why does bash thinks that 010 is 8?
Solution 1:
Number sequences starting with a 0 are interpreted as octal numbers.
Octal 10 = decimal 8.
To get bash to treat it as a decimal number, remove the leading zero or force decimal with:
N=010
N=$((10#$N))
Generally that works for all bases, just replace the 10 with the base that you want:
N=[base#]n