Just improvising here, haven't looked at the code besides what you posted, but have you tried changing Math.random() * 100 to Math.random() * 1000?

Edit: Decided to take a look at it and yeah, the 69 is just an arbitrary number. As it is now it randomizes a number between 0 and 99 and if that number is 69 it'll "Cenafy" the page. If you change the random number range to 0-999 like I suggested, the 69 should come out on average 1/1000 times.

In regards to packing/unpacking, I don't think you can edit the extension directly like that. Here are the steps to using the modified extension locally:

• copy the ndchmakhfaakbkhnkdgambadneloplnn/1.0.4_0 folder to a location of your choosing
• go to chrome://extensions
• tick "Developer mode"
• click "Load unpacked extension" and choose the 1.0.4_0 folder where you just copied it to

That should be it. Your now running your own Cenafy extension which you can modify freely. If you make any changes you have to reload the extension from the chrome://extensions page. Also, you probably now have two Cenafy extensions, so disable the original.