Help with graph apparently showing standard deviation with 2 values?!


I've got a presentation on a scientific paper this afternoon and am very confused with a graph in the paper (graph/dot plot C). I hope this doesn't break forum rules, I do believe this is a statistics question. Basically, in the plot on the far right (C), it shows values +/- standard deviation. However, the SD bars dont cover both values for each dose (x axis). From my understanding, SD with 2 points must be equal by definition as they are both equidistant from their mean.

Is this true, or am i understanding this plot very wrongly?

Many thanks

View attachment 6411
It looks as if the long bar is the mean and the short bars show the SD. If this is the case, then there are a couple of down bars which have been missed by mistake.