I'm adding a 40A breaker to my panel and I'm confused with the corner tabs. I can buy left or right tab breakers that use only one bus bar. I'm guessing the two pole 40A breaker has two tabs, one in each corner/side to catch both bus bars, but I can't see both sides of the breaker in the picture (see link for the breaker below pls). It also looks like I need to move a 15A breaker from the right side to the left to make space but that would make the number of breakers uneven so I would need a plastic cover like the one installed on the right. I'm including pictures of the panel with and without cover, as well as, close up of top and bottom breakers sections. BTW the panel is Challenger and the wiring for the 40A breaker will be going to the bottom of the panel.
Link to breaker: https://www.connecticut-electric.com/40-amp-two-pole-ubitba240