Not a bug Api bug 1 order cancel by user after auto-order submited with balance

Affected Version
3.1 RC20


the other web script connected api with my server example: he have 500$ in my web after connected api 1 order = 100$ his sever api sending 10 order but 5 order submitted x 100$ so his balance now 0$ , but he have cancel button enable on my server, so now he press cancel 1 order so his balance now 100$ and this time instant his api auto-submitted 3 order to my server and now his balance is -200$ ! understand ? also his (Allow Overdrive is disabled)!