2D ising model susceptibility - different values

As I’ve been simulating Ising model in 2D, I searched the Internet for some plots to check whether my simulation is working correctly.

I stumbled upon two versions of magnetic susceptibility vs temperature plots. On the first one (source) the values for a certain $L$ (they are not exactly the same but you can see different tendencies) are much more higher than on the second one (source).

I was wondering why is that? My program produces results as shown on the second graph. Could it be that the first one doesn’t use dimensionless variables?