Your problem lies in trusting the massive development chart. It is full of developing times that suit other people's working processes.

So, is your shadow detail good? Yes? If so, continue shooting at 64 if you like the results.

Too much contrast? You must reduce developing time. Others here (folks whose opinion I'd trust) have posted 12-15 minutes at 68-70 degrees F. Somewhere in that range is a good starting point. After you reach a good baseline, adjust as necessary.

Keep in mind that the light you're shooting in determines everything. If you're shooting in high contrast lighting, shooting at 64 is probably appropriate. If the contrast is low, however, shooting at 64 will give you a muddy mess of mid-tones only, and extremely dense highlights. That's when you want to shoot at a higher EI. Obviously, when you do, developing time must change with it.

Have fun, and remember that it's up to you to figure out how you can alter the results to where you like them.