This is slightly off topic....

I live on a farm, and have a main disconnect switch on the meter pole,
rated at 400A. That feeds 3 buildings (house, garage, and barn) each has
100A main breakers. It also feeds an old 60A fuse panel in a shed. (yea,
that is still fuses but all it does in run a few lights, so I never
changed it).

This is mostly just my home, but I do a little "hobby farming". So my
electrical needs are small. But this was once a large working farm with
large power users, such as huge 240V motors that ran grain dryers on
grain bins.

Anyhow, the pole transformer has been there for ages, and I just noticed
that it's rated at 15KVA. 15KVA is only 62.5 Amps at 240V. (Or 125A at
120V).

Why would the power company install a transformer so under rated?
-OR- Do they rate those transformers in a different manner?

Like I said, it works for my needs, but in winter, I run several
livestock tank heaters and I tell when they kick on by a very slight
momentary (slight) dimming of my lights. (They are rated at either 500W
or 1000W, but there are 9 of them).

From what I am seeing, those transformers are all under rated. A friends
house has 200A service and his transformer is only 8KVA.