The ticket for the baseball games of May 21, 1974, lists the games as 19 & 20 for the Giants. Per a site like baseball-reference they were actually 42 & 43 (and 41 & 42 for the Braves).
The ticket location states Lower Stand Box. Assassin Jerry Schilling (Bill Bixby) and General Robert West (Andrew Duggan) are clearly moderately high into the stands.
The ticket states a starting time of 5:30 p.m. - late in the afternoon with long shadows soon followed by lights. But, most of the footage shows strong, midday natural lighting - signs of a day game.
The black market gunsmith delivers the custom sniper rifle for demonstration and hands it over to the hit man without wiping off his fingerprints. A professional criminal gun dealer would not make that mistake.