“We've only got a couple dozen more to go.”
You're helping your friend mail her wedding invitations. She's sending a lot of invitations, so it's taking a long time. But now you're almost done, so you say this.
We've only got a couple dozen more to go.
"A dozen" means 12. Certain things come in containers of 12, like eggs and doughnuts:
Do you want a dozen or a half-dozen?
We also use "dozen" to talk about numbers that are between 12 and 100. We use "dozens" instead of "tens":
I've been there dozens of times.
There were a few dozen people there.
"A couple dozen" means about 20 to 30.
Use the phrase "have ___ to go" to talk about how much time or distance is remaining before something is finished:
We have three weeks to go before the end of the semester.
I was almost finished - I had another mile or two to go - when my knee gave out.
You can also use "have ___" to go to talk about the number of something that you need to complete:
I have two more sales to go to hit my quota.