Oh my gosh... math isn't my thing either but at least I'm familiar with the units of measurement being discussed. That has to be frustrating!
I was reading over old transcripts so I'm a little behind but in case it hasn't been shared yet - this is all approximate and according to a smartphone app that I've found accurate in the past:
1 yard = a little over 3 feet
1 meter = a little over 3 feet as well (yard's a tiny bit longer)
1 acre = approximately 43,500 feet, and around 14,500 yards
Point being that 400 yards vs. 400 feet vs. 400 acres are all very, very different. If my phone is as "smart" as advertised, I'd say you can probably use yards as meters to get a rough idea of distances.
That said though, I'm very bad at guessing distances as I'm sure many people are, and I think it'd be pretty easy to mis-speak this detail in particular when stressed.