Hi Chinmaya,

I have replied in the support thread regarding the issue. However, as it could be helpful to the other users I will leave a comment below as well.

When the browser spellchecker is used a size attribute is injected by the browser. Currently, the fontSize tool reads the value of the 'size' attribute. However, the values of the size attribute correspond to values such as "x-small", "small", etc. Such values are absolute-size keywords, based on the user's default font size. The Editor does not contain "x-small", "small", etc. in the list of predefined sizes for its fontSize tool. It is also hard to predict what will be the value of "x-small", "small", etc. in pixels. For this reason, in such a case, the value of the size attribute injected by the browser spell correction is displayed in the fontSize dropdown.

The fontSize tool can be configured to use values in pixels. Thus, pixels will be displayed in the tool even after using the browser spellchecker.

tools: [              
        {
                name: "fontSize",
                items: [
                  { text: "8px",  value: "8px" },
                  { text: "14px", value: "14px" },
                  { text: "16px", value: "16px" },
                  { text: "20px", value: "20px" }
                ]
        }
]

Dojo with sample configuration is linked here.

Regards,
Neli
Progress Telerik