If I may suggest You to use the C/AL Symbol Menu (F5), combined with the help (F1), while in design-mode, You’ll be able to find a lot of help on the syntax of C/AL.
For this You need to define CONVERSION as SumIndexField on one of the keys in the source-table.
Text0001/0002 are “Text Constants” you define in the “C/AL Globals” menu option, you can accede there when you are editing the “C/AL Code” of your object (table, form…). For example you can assign to Text0001 the text 'The value of the conversion is:"…
when you will write the message “MESSAGE(Text0001 %1, CONVERSION)” it would appear something like:
But…
The %1 needs to be either “inside” the text-var (e.g. Text001 - ‘The value of the conversion is: %1’), or You need to do it as adding another text-string to Text001 (e.g. MESSAGE(Text001 + ’ %1’,CONVERSION))
Just thought I would add a point here. The reason for these Text constants is to allow the use of MultiLanguage in Navision.
Even thought you may develop in only one language it is still standard to use these Text Constants, and I personally think it makes your code look neater.