To determine how many of the statements about the doctrine of "procedure established by law" in the Indian Constitution are correct, let's analyze each statement:

1. Statement I: It protects against executive action.

   Explanation: The phrase "procedure established by law" is typically interpreted to mean that as long as a law is properly enacted, state action is justified. This principle primarily focuses on legislative actions rather than executive actions. Hence, this statement is incorrect in the specific context of protecting against executive action.

2. Statement II: It protects against legislative action.

   Explanation: The doctrine of "procedure established by law" essentially ensures that no person is deprived of life or personal liberty unless there is a law enacted by the legislature prescribing a procedure. Therefore, it does address legislative actions. Thus, this statement is correct.

3. Statement III: Article 22 was incorporated into the Constitution as additional safeguards after debate in the Constituent Assembly.

   Explanation: Article 22 provides for protection against arbitrary arrest and detention. It indeed was incorporated as a part of fundamental rights concerning protection against arrest and detention. This statement is correct.

4. Statement IV: In the Bank Nationalisation Case, the Supreme Court adopted its strict interpretation.

   Explanation: The Bank Nationalisation Case (R. C. Cooper vs. Union of India) is known for interpreting property rights rather than the doctrine of "procedure established by law." Moreover, this case led to a broader interpretation concerning life and liberty rights (Article 21), comparing it often with "due process of law" rather than applying strict interpretation. Therefore, this statement is incorrect.

Conclusion: Based on the analysis, we find that Statements II and III are correct, making only 2 statements correct out of the four provided.