Laid off in March, there's a four-month gap on my resume now, and I don't know how much to say about it

The layoff wasn't performance-related, it was forty people in one afternoon, but explaining that in an interview without sounding defensive is harder than I expected. I've had two recruiter calls now where the gap came up and I could feel myself over-explaining, adding detail nobody asked for. I've used the time to finish a project and do a lot of interview prep, which I think is a fine answer, but I say it and then keep talking anyway. How do you say "there was a layoff" once and then just stop?