Hello Ursus,
Ok you can also not open a dialog box and just input the value 10. The add new variable - is if you want to make this a selectable value (global) when you start the strategy. I.e on this historical test you might try 10 , next time you might try 9.
With variables there are many types of variable - I'd say click the help and do a lot of reading to get your mind around it!
If you want we can always work on a system together - you say your idea, and i'll build it step by step. But keep it simple lol I charge for complex
DoC