TTFB score

Hello!

I cannot understand how retrieve “First Byte Time (back-end processing)” from response I get in API request. I tried to calculate the value by using the next formula:

Target First Byte Time / First Byte Time * 100

but it also got me wrong value. Please help me understand how I can get value exactly the same what you have in that filed?!

Image attached to see exactly what field I want to get

That’s a score, not a measurement - you sure you want the score? The measurement is going to be much more reliable.