[SOLVED] Campaigns discount not accept two-digit numbers

I can't apply a discount greater than 9% when creating a campaign. The "-%" field does not accept two-digit numbers. Why?

LiteCart® 2.3.3

That's really strange. 
This morning the tests on this Campaigns discount function with the three main browsers (Chrome - Edge - Firefox) were successful and this stranger quantity limitation defect no longer appeared. 
But now the spontaneous question: Are these calculations influenced in any way by the WAN or the operating environment? Because I really can't think of any other cause.

I have no idea. Browser extensions?

I have only AV applications on my browsers (on my win10 system) loaded; only the Bitdefender Total Security and its components act on the browsers. It's certainly a invasive app but for blocking a calculation function seems unlikely to me.