GST refund on school uniform

shivam jain (student a final) (7 Points)

02 June 2021  
if I m a school uniform manufacturer.
I pay gst as input tax @ 12 % on purchase of yarn.
and I collect gst as output tax @ 5% on sale of school uniforms .
then how this difference of 7% can be claimed as refund .?
please explain .
thanks in advance .