UVB bulb for last 2-4 weeks of flowering.

Hey just wondering what UVB bulbs are appropriate for increasing cannabinoids/terpenes during late flower?

1) I noticed there is 2.0 UVB, 5.0 UVB, 10.0 UVB AND 20.0 UVB on Amazon. Is this number important for selecting a bulb?

2) I run 2 400w HPS in flower. What wattage is appropriate to complement the bulbs I am using?

3) What distance from the canopy would you place a UVB bulb?

This answered most of my questions.