Problems with allocated partition

Good morning everybody

First excuse my poor English but i'm sure you'll understand me.

I' m using cloners since  Ghost before Symantec. A long time ago

Then ten years using Drive Image. Also tested Acronis.

Now using Windows 7  cloner inside. All's fine with cloners 20 years long

Aomei have been recommended  by a famous French Site. Aomei is really very interessant.

But somthing is wrong. I explain.

I have 4 HD and eleven partitions. I  choose a  partition  S:  96 Go  as a target.

I format it.   As usual since 1998. OK. It's quite empty. 96 Mo free.

I start  AOMEI   Assistant.  Quick copy partition. I want to copy C. 100 Go.

I remember using Drive Image that the clone is 50% smaller.  Clone 50 Go finally. Good.

But Aomei refuse the target because it' allocated. All my eleven partitions are allocated.

What's the probleme ?  I had always do like that  since Ghost, Drive Image, Acronis and Window 7.

Something simple to do ?  I want to keep all my partitions like that.  And I do not want operate dangerous actions.

Thanks a lot.