List of plus bonuses in Puzzle & Dragons: Super Mario Bros. Edition
From the Super Mario Wiki
When the player powers up a teammate in Puzzle & Dragons: Super Mario Bros. Edition at the Power Up spot at Toad Houses, they may sometimes earn plus stats next to their current stats in the form of stars. Pluses, or stars, are additional stats that a teammte can earn outside of leveling up. The amount of increase is dependent on the stat: +10 for HP, +5 for ATK, and +3 for RCV. Each teammate may have up to 297 plus stats, with 99 per stat. This means, via pluses, a teammate can have their HP increased by up to 990, up to 495 for ATK, and up to 297 for RCV.
Each depowered teammate has a 20-25% chance to produce a plus. When transferring power to a teammate of the same attribute, the chance of that depowered teammate producing a plus doubles. Each type of teammate always produces a plus in the same stat, shown in the charts below. Depowering a teammate with pluses causes those pluses to be transferred to the teammate being powered up. For this reason, it's recommended to depower a teammate for their pluses to another teammate of the same attribute, then with the accumulated pluses, to power up yet another teammate that may not necessarily share the same attribute type. For example, if the player depowers many Goombas for their ATK pluses to a Wiggler (both allies wood-types), then transfers those pluses to a different attribute teammate - such as a Cheep Chomp, a water-type ally - by depowering the Wiggler, the Cheep Chomp would receive roughly double the pluses than they would if the player directly depowers the Goombas for them. Using this method, the player can strengthen allies where their stats may be lacking (i.e. using HP pluses to raise a teammate's low HP).
This page lists which teammates produce which plus stats for other teammates being powered up.