Please help me Regarding I-94 Doubt

[g.chandan]

Hi All
I am on a B1 - Visa visited 4 times to USA.But last time (4th time) i over stayed for about 20 days after the i-94 expired. Normally first 3 times they gave i-94 for 3 months, last time it is only for 2 months, so it's my mistake i haven't looked it till iam back. All this happened in June 2009. Now i am aproved for H1 - B for the year 2010. I need to face a visa interview. In DS 156 Application, Question No 38. ( Have you ever voilated the terms of a U.S. Visa or Been unlawfully present in,........)
I am checking the option Yes. Can you all help me in this please. Does 20 days extra stay will effect my H1 - B visa or if i get the Visa, when i go to USA on H1 - B Visa does immigration stop me. Please help me on this case. Thanks a lot for all your help.