It's easy to tell them apart by color and by checking your indicator setting.
First, look at the filter itself. A Brita LONGLAST filter is blue. A standard Brita filter is white.
Second, you can check what mode your filter change indicator is set to. Press the STATUS button for 1 second and release. The light that blinks corresponds to your current filter mode. If the green light next to LONGLAST FILTER blinks, it's set for a blue filter (120-gallon life). If the green light next to STANDARD FILTER blinks, it's set for a white filter (40-gallon life).
If the mode is wrong for the filter you actually installed, you need to reset it. Hold the STATUS button for 6 seconds for a LONGLAST filter, or 2 seconds for a standard filter, until the correct green light blinks three times.
Using the wrong mode will cause the indicator to give you inaccurate replacement reminders.