Suunto D6 User Manual page 64

Decompression will now begin, but is very slow. You should therefore continue your
ascent.
Display at the ceiling zone
When you reach the ceiling zone, the display will show you two arrows pointing at
each other (the "hour glass" icon). Below is an example of a decompression dive at
the ceiling zone.
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UPWARD POINTING ARROW HAS
DISAPPEARED AND ASC TIME LABEL HAS
STOPPED BLINKING, MEANING YOU ARE IN
THE DECOMPRESSION RANGE.
TWO ARROWS POINT AT EACH OTHER
"HOUR GLASS" . YOU ARE IN THE OPTIMUM CEILING
ZONE AT 3 M. AND YOUR MINIMUM ASCENT TIME IS
8 MINUTES.