Here's what Social Security says:
Earnings for active duty military service or active duty training have been covered under Social Security since 1957. Social Security has covered inactive duty service in the armed forces reserves (such as weekend drills) since 1988. If you served in the military before 1957, you didn’t pay Social Security taxes, but we gave you special credit for some of your service. You can get both Social Security benefits and military retirement. Generally, there is no reduction of Social Security benefits because of your military retirement benefits. You’ll get your full Social Security benefit based on your earnings.
So for most people claiming benefits now, military pensions are from employment covered by Social Security and so should not be entered on the Non-Covered Pensions screen. You can confirm this by referring to your Social Security statement and making sure that the earnings your military pension is based on were taxed by Social Security.