The selected View type is indicated.
The available views are:

SLM is a traditional Sound Level Meter view.
L(f) is a spectrum with frequency filters and weighting networks.
L(t) is a profile of any of the measured filters or networks.
Ln is a statistical distribution display.
FFT is a narrow band spectrum based on linear frequency level analysis.

Landscape mode are also available, selecting the the views with "Landscape" behind.