A math lesson to remember

“I was good at maths,” Lew said, casually.
“You what?” I blurted,
“Didn’t I tell you? When I was in the artillery, I calculated gun angles, so the shell would land on the target. Six guns, I had. Different elevations, different targets, distances... Lot of things to take into account. Logarithms – did all the calculations an’ that in my head. We had a contest. I had my guns set up and ready to fire when everyone else was farting about trying to calculate the range. I won. Monty himself came up to me personally, congratulated me, he did.”
“You never told me.”
“About Montgomery?”
“About the math.”
“It was a long time ago. Mind you, I can still do all your mother’s bets.”