IUI only 6 hours after trigger shot

Melanie
Ladies, i have my first IUI scheduled for tomorrow. They checked my follies today and the largest onevis only 19 mm. Since they want it to be at 20, they will give me the trigger shot tomorrow. My hubby is traveling Wednesday so they decided to do the IUI 6 hours apart from the trigger. Everything i read online says 24 to 36 hours from trigger. I am so confused. Has anyone else had a trigger that close to the IUI - and what were your results. I feel i ameasting this month... I am 39 and dont have much time left... We are trying since 4 years...