Jeppesen FliteDeck 3 - Manual (Page 163)

JeppView FliteDeck User's Guide
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When you select a chart that is not currently in the Clipboard, the Previous Chart
and Next Chart buttons are not available. This occurs because the Next Chart and
Previous Chart labels depend on the selected chart in the Clipboard. To view the
clipboard charts, either add the displayed chart to the Clipboard, or select a chart to
view from the Clipboard.
NOTE
There is no underlying meaning to the bold text that occasionally occurs
in the Previous Chart and Next Chart labels. This is a result of how the
program analyzes the size of the text and the size of the buttons.