@rajesh2373 – the text frame was scaled.
The actual point size is 21.6 pt, the original point size (before scaling) is 18 pt.
If a paragraph style is involved, you cannot see a change in the paragraph style panel (usually indicated with a + at the end of the paragraph style name).
To prevent this you could:
1. Set different preferences at:
General / When Scaling / Apply to Content
or for the single case:
2. Use the Transform Panel and its options with "Redefine Scaling as 100%"