Negative numbers with Spin do not work properly

Hello Together

I hope that someone can help me.
I don’t know if my problem is a bug or if I am doing something wrong.

I have a control. In this control I have a field of type Integer. The field is not bound to a DB.

For this field I have activated the spin. Furthermore I allow positive and negative numbers.

If I now test the whole thing I see the field and can increase/decrease the value with the arrow up/down. So far so good.

But if I select a minus number (-4) and then click somewhere else, the number automatically changes to a positive number. (4)
If I then change the number again to a negative number (-4), it remains so.

It is also recognized as a negative number in the rest of the program.

But what I don’t understand is why it is changed from a negative number to a positive one the first time.
If a user doesn’t know this and doesn’t pay attention, it can unfortunately happen that he achieves the opposite of what he wanted…

Can someone tell me if I’m doing something wrong or if this is a bug?

Thank you!