You are right, we don't know. I was writing from memory late last night & didn't go back to check the text.

In fact, I think 7 years were Anne's "more rigid requisitions" which were never even proposed when Lady Russell's plan was rejected.

"If we can persuade your father to all this," said Lady Russell, looking over [Anne's] paper, "much may be done. If he will adopt these regulations, in seven years he will be clear. ...

How Anne's more rigid requisitions might have been taken is of little consequence. Lady Russell's had no success at all".