Fix: typos in data_flow_issuance.md

[naonishijima]

• Delete duplicate lines
• Add missing mod n

Signed-off-by: Nao Nishijima nao.nishijima.xt@hitachi.com

[swcurran]

@whalelephant -- I think this looks good, but would appreciate you double checking.

Or @mikelodder7, perhaps you could verify.

Thanks

[whalelephant]

LGTM!