Recently i created a bootable windows installer using RUFUS. after doing it i saw that it is now 29.4 GB, how can i restore it back to 32 GB?

Recently i created a bootable windows installer using RUFUS. after doing it i saw that it is now 29.4 GB, how can i restore it back to 32 GB?

You fell victim to the marketing slogans illustrated by this WikiPedia article.
So, according to the definition in the above link, your drive probably has a capacity of
32GB (32*1000*1000*1000 bytes)
But because the free space is calculated in GiB, the real capacity is
32,000,000,000 / (1024*1024*1024) = 29.80 GiB (gibibyte)
The rest of the difference may be due to filesystem overhead and such.