  The sudden spin-down in the rotation of magnetar 1E 2259+586 observed by
Archibald et al. (2013) was a rare event. However this particular event,
referred to as an anti-glitch, was followed by another event which Archibald et
al. (2013) suggested could either be a conventional glitch or another
anti-glitch. Although there is no accompanied radiation activity or pulse
profile change, there is decisive evidence for the existence of the second
timing event, judging from the timing data. We apply Bayesian Model Selection
to quantitatively determine which of these possibilities better explains the
observed data. We show that the observed data strongly supports the presence of
two successive anti-glitches with a Bayes Factor, often called the odds ratio,
greater than 40. Furthermore, we show that the second anti-gtlich has an
associated frequency change $\Delta\nu$ of $-8.2 \times 10^{-8}$ Hz. We discuss
the implications of these results for possible physical mechanisms behind this
anti-glitch.
