If they are both fertile, I would count on kits in a little over 100 days.
Now, you say you saw a plug last month and one this month ... there may be a bit of a problem ... if both breedings 'took'.
Chinchilla females have two and can be pregnant in both sides at one time. If a female gets pregnant in only one side, she will go back into season at the regular time and can get pregnant in the other side. This is called superfoetation. The problem here is that the due dates are to far a part and when the momma chin goes into labor, more than likely, she will deliver both at the same time. The second one will probably be a still birth, or will not live more than 24 hours ... as a general rule. The way to tell which one is which is to note the size of the two kits ... one will be much larger than the other. Rarely is the second one large enough to survive, and/or if it does survive, it will usually pass away within the first year because it was not fully developed before being delivered.
I will post a picture of a pair of kits born to a pair in my herd. Both were born the same day, from the same momma ... but they were conceived at different times.
Jo Ann