Unable to get back my original pen drive capacity

i created a bootable usb flash drive for dell diagnostics using my 4gb pendrive. after creation the size reduced to 1.96 gb. it was mentioned that after reformating the size will be back to normal. but even after reformatting nothin happened. can anyone plz tell me how to get back my initial capacity of 4 gb
 
if you have already reformatted (ie deleted the bootable info), then
  1. get the Disk Manager
  2. delete the partition(s)
  3. add ONE partition
  4. then reformat
 
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