In the the paper "Efficient Methods for Conversion and Solution of Sparse Systems of Low-Degree Multivariate Polynomials over GF(2) via SAT-Solvers" there is a Figure that I can not understand and I need help to understand it. The authors plot the running time of the probability distribution of the SAT solver applied to a certain problem. My question is about the X axis. Why there are numbers in this Figure 1, that are placed in vertical form? How to interpret this axis X?
I imagine that are interval times but I do not understand why they are in vertical form. Moreover, on the same axis there are twice the number 180.