The grating is defined as having 3.5x10^3 lines per meter so it has a potential error of 0.1x10^3 lines per meter. It is defined to one decimal place If it was less than 3.45x10^3 it would have been written as 3.4x10^3 and if was more than 3.55x10^3 it would have been written as 3.6x10^3. So, the measurement can vary between 3.45x10^3 and 3.55x10^3 i.e 0.1x10^3 lines per meter.
As for the 0.135m, sorry, this should be 0.13m. This is the distance between the first maxima and the last on the interference pattern. The first line is centered around 0.6cm on the ruler and the last is at 13.6cm. If you put this into the equation you get d=3x10^-4m so the no. of lines per meter = 3.34x10^3 - I really should double check things before posting !!