Hi Rickooreo.
How many questions you can miss to score V40 on the GMAT ranges from 3 to 10 counted questions.
There are also 6 experimental questions on the verbal section, and you could miss all of them, but since you won't be aware of which questions are experimental, it doesn't make sense to plan to miss them.
Most people who score V40 miss around 5 or 6 counted questions.
So, basically, to score V40, you have to get around 24/30 to 25/30 counted verbal questions correct, or about 80 to 83 percent of the medium and hard questions you see. If you are scoring V40, you won't see any counted easy verbal questions.
If you want to consider all the verbal questions, including experimental questions, in your calculation, you could think of the goal as to get 83 percent of the questions, which is 30 questions, correct.
For V41 just add one more correct question or one less missed question to everything above.
Ideally, you'd miss only hard questions and get all the medium questions you see on the test correct.
So, when practicing, to achieve V40 to V41, shoot for close to 100 percent of easy, 90 to 100 percent of medium and at least 70 percent of hard practice questions correct.
For more on how to practice to achieve a V40+ score, see this post.
The Best GMAT Practice Methods