There are a lot of government colleges in India , so to tell how many total seats are there in government colleges in India it would be difficult.  I would like to make aware of the fact that there are approx 10 thousand seats in IITs and about 20 thousand seats in the NITs . Also there are some reputed colleges which are state funded such as DTU and NSIT . So there would be approximately 50 thousand seats of the colleges which are considered to be grade A colleges.

Hello ashish... 

It is not mentioned anywhere that how many students is selected for government colleges for engineering..... 

It's depend on the student ability who crack the government examinations... 

After selected In the examination, students get admission in the best government colleges.. 

Hello,
Each year by jee mains rank seats in government colleges like NITs IIITs and GFTIs are filled upto 50 k.
Also after 25k it becomes very hard for general category students to get a seat. You can see the cutoff for various government colleges in this link

https://www.google.com/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/articles/jee-main-cutoff/amp&ved=2ahUKEwigleqFrL3iAhUM63MBHczNBsIQFjAAegQIAhAB&usg=AOvVaw0ay0p7xaI0Sc82xeEH0ED5&ampcf=1