Change the spelling options

In Options menu click Spelling. Spelling options dialog will be showed

Select appropriate options. Press Ok button. The default values can be selected using Default button. The options will be persisted after the program quitting

Here is several options

Limit of suggestions in menu
The maximum count of entries for the suggestion menu. The option value is a number in the range from 5 to 50. The default value is 15
Limit of suggestions in dialog
The maximum count of entries for the suggestion list in the spell checker dialog. The option value is a number in the range from 5 to 500. The default value is 40
Auto spelling mode
Automatic checking of the spelling in the text, By default is turned on
Case sensitive
Set whether the spell checker is case-sensitive. By default is turned on
Ignore all caps words
Set words that are entirely in uppercase should be ignored for spell checking. By default is turned on
Ignore capitalization
Set whether capitalized words should be correct if the word in the dictionary as lower-case. By default is turned on
Ignore words with numbers
Set if words that include a number in any position should be ignored for spell checking. By default is turned on