Prepare a large list of vocabulary the students should know or have been studying, for example animals. Some new words are okay too, but don't make them tired of learning new words.

Make a large B4 sheet with all of the pictures from your list. There should be any number of items grouped together for the students to count. There could be 4 cats together, 2 cows, or a snake. They must be grouped together.

Make teams of 4 or 5. Practice all of the words in the list using large A4 flash cards. Give the sheet to them after practicing the vocabulary and the students have two minutes to memorize all of the numbers for each item in the paper you prepared.

After two minutes, take the sheet away. The NET (Native English Teacher) has the students put their hands on their desk. The NET then says "How many _______?" and the first student to put up their hand (or use the buzzer) has a chance to answer.
The student should use full sentences with correct pluralization (if they have been taught it already).
For example, "How many cows?" -- "There are two cows."

The students must make big hand movements. It's difficult for the teacher to notice small movements. Having two other JETs (Japanese English Teachers) is perfect to help see who was first. When it's not clear who was first, the teams should play rock-scissors-paper to have a go. Sometimes is necessary to just skip that item and continue.

The team with the most points, after all items have been guessed, wins.