258 = very interesting. 2 being v, you sign “very”, and then using 5 into 8 from ahead of your face/nose area for “interest” sign.
And for 84, try and sign it kinda side way. Kinda like “terrible” sign, but you would say it after crazy or whatever happened.
Like “oh really? 84!”
I was referring to ASL, what’s your sign language?