Update help documents

Update the following help documents:

• 04 _ Search List of Directories.help.md: Add instruction on limiting the time period to plot
• 40 _ Firmware Notice.help.md: Update list of channels affected by the old Pegasus firmware versions problem and add instruction on how to fix the problem

sohstationviewer/documentation/40 _ Firmware Notice.help.md

@@ -13,5 +13,6 @@ These channels included:
 
 Currently, SOHViewer only supports new versions of the Pegasus firmware. If the 
 plotted values of the channels listed above are higher than expected, the data 
-is recorded using old firmwares. If this happens, the affected channels can be 
-edited to reflect the old units (refer to the View-Edit Database Tables section).
+is recorded using old firmwares. This problem can be fixed by editing the 
+affected channels' conversion factor to reflect the old units (refer to the 
+View-Edit Database Tables section).