H1B, H4 Visa

Hello Everyone

i have some issue about certain question that i was asking my self for my interview was schedule for this month and im lil nervous.

first question was that im imagine if the VO Ask how long im i working now in the company
the real isssue is that it was now a year and 6mths, which is complete 18months

so i wonder can i answer 1 and half year, or i should use the speech 18months OR better said 2 years ?

help me please because on my last interview in the month of september when the VO ask me this

vo: HOW LONG HAVE YOU BEEN WORKING IN YOUR CURRENT WORKPLACE ?

me: I began gave the date, month,year, that i started work (I M WORK THERE SINCE JUL,01,2016)

 without finish speaking VO interupt me by saying Ooh! stop you are not qualify.
and when im out of the embassy i blame my self why i using the date

so today i dont want to comit the same error cause it may be what that disquqlify me that day.

help me.