Might be bug - I don't know.

If not...

You only have these siege points as long as you have the siege.

Also..

week 1... you have 100 (10000 points) 

week is over.. new week started...

so week 2... you now recall because you need the troops to maybe win the siege ranking again... but the game resets your points to 0 when a new week starts... so if you recall these troops now... you are -10000.

I hope it make sense, or that agent solve your bug!

Have a nice day! 

the answer that our friend Coeius gives us is correct, thank you.

If it is what happens to you it is not a bug, waiting for your comment friend Unknow

Yep, I can also confirm that Coeus is right.

Hello!

The weekly ranking is updated every Monday at 7:00 AM UTC. At that time all Siege points earned last week are reset back to 0. Hence, when you start recalling troops from the besieged cities, each time you get -100 Siege points.

Therefore, having finished the recalling of your troops from the besieged cities, first, you need to besiege some new cities and earn Sige points to reach 0 value. After that, all further Sieges will be bringing you Siege points for your current Weekly Ranking.

Either you can wait a week until the next Monday when your current negative value of the Sige points will be reset to 0 automatically.