That tool was designed to SELL batteries, not test them. Show a customer a very low voltage reading on a low or discharged battery, then sell him a new one. Then recharge the trade-in (all it needed anyway) and sell it as a "rebuilt" battery at half the price of a new one! In the days of 6 volt batteries that ran low frequently because of poor charging system operation, it was a very common practice among unscrupulous retailers!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!