Hint: it's a joke.

You are free to read a graph on any direction you want.

You can move back in time using this device we call "memory". Up and to the left - value grows as you consider earlier values. Up and to the right - value grows as you consider newer values. Yes considering newer values after older ones is a reasonable default but it's not completely redundant to specify that's what's meant.

Have you ever done one of those DNA kits? I feel as though you might have some Vulcan in you.