Apart from monitoring the backlink profile growth, SEO SpyGlass allows you to keep track of the changes that may influence spikes or drops in the number of backlinks, with the help of the Events feature.
To Add an event in an SEO SpyGlass project, go to Preferences > Events and click Add. Select the date the event took place, describe it in brief. Additionally, choose whether the event referes to the current project only (for instance, you've just published a piece of content that's likely to attract backlinks naturally), or if it's a global event common for all projects (like Google's update rollout or drastic changes in your niche).
Events can be added, edited or removed at any time. Keeping track of your SEO/SEM activities and changes in the SEO industry / business niche, you can get a better understanding of what influences your backlink profile, be it growth or drawdown, by matching the spikes on the progress graph to the events dates.