This chart helps you answer the question "how hard (IF) should I ride?"
The major determinant of how hard you should ride is how long you are going to ride.
To use this chart, you need to be able to ballpark your bike leg time. If you can't or won't do that, don't use the chart.
If you do what you suggest, ride at the IF of your recent ride, the chart says that you have absolutely zero chance of finishing the race (unless you find a way to finish the bike leg in about 2 hours probably, but that's off the chart).
Even if you can say that you'll likely ride between, for example, 5 and 6 hours, you can obtain from the chart the range of IFs that you may want to target and it won't be that wide of a range.
Then, try that IF range for large segments of long rides and then run a bit after the ride and see how it all goes.
Note that an IF of 0.89 for almost 4 hours raises a bit of a flag that your FTP may be quite a bit higher than you think it is.
The major determinant of how hard you should ride is how long you are going to ride.
To use this chart, you need to be able to ballpark your bike leg time. If you can't or won't do that, don't use the chart.
If you do what you suggest, ride at the IF of your recent ride, the chart says that you have absolutely zero chance of finishing the race (unless you find a way to finish the bike leg in about 2 hours probably, but that's off the chart).
Even if you can say that you'll likely ride between, for example, 5 and 6 hours, you can obtain from the chart the range of IFs that you may want to target and it won't be that wide of a range.
Then, try that IF range for large segments of long rides and then run a bit after the ride and see how it all goes.
Note that an IF of 0.89 for almost 4 hours raises a bit of a flag that your FTP may be quite a bit higher than you think it is.