In blackjack using the hi-low counting system, why does the illustrious 18 say to stand 16 v 10 on a 0 count?

Obviously surrendering is not an option. I would think basic strategy would be based on the uption of a 0 count. So why does this index suggest to alter play on a 0 count. Same thing applies to a 12 v 4 when the I18 suggests to hit on a 0 count.