There are many metaphors and idioms in Japanese that are fun and useful.
This idiom is used to say someone is lying about their age!
Let's learn a useful Japanese idiom
鯖（さば）を読む
saba o yomu
(Literal meaning) = To read a mackerel
(Idiomatic meaning) = To manipulate figures to one's advantage
◆ Etymologyexplanation
The origin of the word "saba" is said to have come from the fact that mackerel was a fragile fish and was counted quickly because there were so many of them, which did not match the actual number of fish.
◆ How do you use it?
Watch this fun video to see how you use it in conversation