Don't quote me the 'auto' option applying peak normalization, but it's a reasonable assumption. From the VP FAQ...
Normalize
To 'normalize' is to adjust the volume so that the loudest peak is equal to (or a percentage of) the maximum signal that can be used in digital audio. Usually you normalize files to 100% as the last stage in production to make it the loudest possible without distortion. Another reason to normalize is to have multiple tracks sound equally loud, or to have equal average loudness.
The 'Peak' normalization method finds the sample of the greatest magnitude within the file. Normalization is then done with this value as the peak. With the Normalize Peak Level set to 100% (0dB), the whole file will be amplified so that the peak reaches 0dB.
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For more insight query the company... https://tinyurl.com/r89tpcw
Here's a related read... https://emastered.com/blog/lufs-vs-db