RRD remove Logarithmic scale


I have added a Count Sensor graph to the Dashboard, which contains a few metrics. However, although each individual metrics is presented with linear scale at the Sensors tab, they are show as logarithmic when put into a single graph:

I know it is related to the “-o” option that is appearing in the current rrdtool command, but how can I disable that?
Also, could someone please help me increasing the legend text max size?