Update README.md

Docs/CodeElements/README.md

@@ -133,6 +133,9 @@ following the order of **LEFT** <span>&rarr;</span> **TOP** <span>&rarr;</span>
 <p align="center">
 <img src="./images/IO_Groups.png" width= "1600"/>
 </p>
+<p align="center">
+Figure 2.  Illustration of grouping IO ports.  
+</p>
 
 - Group the closely-related standard cells,
 which connect to the same macro or the same IO cluster.
@@ -240,7 +243,7 @@ in these clusters corresponds to an entry of the .fix file. The cluster id start
 <img src="./images/net_model.png" width= "600"/>
 </p>
 <p align="center">
- Figure 1.  Illustration of net model used in Circuit Training.  
+ Figure 3.  Illustration of net model used in Circuit Training.  
 </p>
                                      
 
@@ -263,7 +266,7 @@ The following figure shows an example: the left part shows the cluster *c<sub>1<
 <img src="./images/breakup.png" width= "1600"/>
 </p>
 <p align="center">
- Figure 2.  Illustration of breaking up a cluster.  
+Figure 4.  Illustration of breaking up a cluster.  
 </p>
 Note that since the netlist is generated by physical-aware synthesis, we know the (x, y) coordinate for each instance.