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Credit is Due Where Credit Is Due

First, you want to visit your played games. You can do so by visiting this Link.

Then scroll down to Halo Reach, if you have a lot of games and don't want to find it,
and are running Google Chrome hit ctrl+f, and type halo.

Check your last played date,

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(Mine was 161 days ago, which allowed me to gain 160,000 credits.)

Then calculate the difference from today, and that day.
You can that through this site [ Register or Signin to view external links. ]

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Mine was, again, 161 days.

Then open Horizon, as well as the Halo Reach credit editor.

Open your profile.

For the number of credits you want to add, insert a number before your given one.
(Mine was 161, so I put 160000) then click add.

Save, rehash, and resign.

start up Reach(OFFLINE) and wallah look at dem credits.
Then connect to Xbox Live, and they should be there.

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Also if you last played a day ago then you'll still only get 1000 credits.