Following UMG UI Designer quick guide but can't get Ammo to decrease, Why?

UMG UI designer quick start guide page 1 part 5-6, I’m following the guide and so far everything has gone right up to the end of page1, I can lose health and energy, except my ammo isn’t decreasing when I shoot, I’ve tried fixing it but can’t; think it has to do with the part I wrote at the start, does anyone know what I’m doing wrong?

It looks like you are setting ammo to -1 rather than subtracting 1 from it.

That’s the only thing that immediately jumps out to me. If that doesn’t help let me know.