Question about the 50k FIF rule

Is it 50k total costs of investments you currently hold. Or is it 50k worth of costs for any foreign investments you have ever held.

For example. If I have spent 45k on a FIF. And I want to sell all of it and then invest 45k into a different FIF. Do I then have a cost of 90k for FIF and have to pay FIF tax. Or is my FIF cost still considered 45k, because that's the cost of my currently held asset.