Why two sanitizers cannot kill virus 100% when they both can kill 99.99%

TV advertisements on sanitizers and soaps always claim on killing 99.99% germs. So a common question arises why can't the remaining .01 %  be killed by using another sanitizer same time. 

 

Well it's a very simple reasoning, the other sanitizers too claim that they can kill only up-to 99.99% of viruses. 

 

So in a random experiment, if one uses two different 

sanitizers in same wash. In it's best case scenario, the first sanitizer/soap kills 99.99% viruses, similarly the second sanitizer too as per it's claims gives it's best performance too, and kills 99.99%  of the remaining .01% viruses.

So 99.99% of remaining .01 is still 1/9999 or roughly = .00010001000.

So if one uses two sanitizers and both works at their max claimed performance , the total killed viruses will be 99.99 +.0001 = 99.9901 which is still not 100%.

Isn't the math simple ?

Disclaimer : its an attempt to write a mathematical satire