Downwards 74LS190 with clock wired to another's RCO counts twice
What's wrong is that You're using RCO\ from U2 to clock U5, when you should be using U2 RCO\ to enable U5.  

You can fix the problem by connecting U2-11 to U5-4 and parallel clocking both counters as shown in the red box, below.

The legend for Figure 2 is wrong, since what's shown is the way to cascade either '190 or '191 counters using RC\ and CE\ .