update readme

Author: fbchen

README.md

@@ -6,8 +6,8 @@ No matter how complex the layout is and how deep the constraints are, it has alm
 performance as Flex and Stack. When facing complex layouts, it provides better performance,
 flexibility, and a very flat code hierarchy than Flex and Stack. Say no to 'nesting hell'.
 
-**It is recommended to use ConstraintLayout at the top level. For extremely complex layout(A
-thousand child elements, a thousand constraints), layout and drawing total time within 5
+**It is recommended to use ConstraintLayout at the top level. For extremely complex layout(One
+thousand child elements, two thousand constraints), layout and drawing total time within 5
 milliseconds（debug mode on Windows 10，release mode take less time）, the frame rate can be easily
 reached 200 fps.**