What this game trains
Number Rush is the plainest possible test of numeric entry: one value on screen, one chance to reproduce it, then the next. Because the values are drawn from the same pool your difficulty setting uses everywhere on the site, moving from Beginner two-digit numbers up to Expert eleven-digit decimals gives you a fairly honest picture of where your reading and keying speed starts to fall apart.
Each match adds ten points and each miss removes five, so the score you finish with reflects the balance between how quickly you key and how often you are wrong — not raw volume.
What to focus on
Read the whole value before you begin keying. Most errors in this game come from starting to type after glancing at the first two or three digits and then guessing at the tail. Keep your eyes on the display and your fingers anchored on the 5 key so you never look down to reorient.
If your accuracy sits below about 95 percent, drop a difficulty level rather than pushing through. Speed built on a shaky pattern of corrections rarely transfers to real work.