The details
The rollout ran from the morning of August 18 to the early hours of August 21, Pacific time, which makes it one of Google's shorter updates. Google logged it on its status dashboard as a global change. According to industry reporting, Google did not publish a companion blog post or announce any new spam policy, and a spokesperson said the update was not aimed at link spam or site reputation abuse in particular.
The background
Ranking tools had already recorded unsettled results earlier in the month, around August 5 to 6 and again on August 12 to 13, with no confirmed update behind them. Movement continued after the spam update finished, so a change in your numbers during August is not automatically the spam update.
Our read
For a genuine local business this was a quiet event. The sites that report losses after spam updates are usually built on volume: hundreds of near-identical pages, purchased links, or content written for search engines instead of customers. If that describes part of your site, fix it because it is a risk at every update. Recovery from a spam update can take months, as Google's systems need to see the site comply over time.