Hello Oksana!
Sorry to hear that this was a bit difficult. If there is anything else troubling you about this question, please don't hesitate to ask, and a subject expert will gladly help you :)
When you see WT, it is referring to Wild Type.
For W140L, that's exactly what you are describing! W is substituted for L at position 140.
Hope that was helpful!
Cheers,
Molly