As of September 2018, Instagram will begin to send login notification emails when you login with a new device for the first time. This also applies if you login using Flume.
As long as the location, device, and time of log in match when you logged in with Flume, there is nothing to worry about. If these details do not match, please secure your account and change your Instagram account password immediately.
* If you reset Flume, the next time you log in with your accounts, you will receive another one of these emails.