The phrase "specific button" refers to a particular button among a group of buttons. It means that there is one button out of many that you need to press or use for a particular purpose. Full definition
Attack requires specific button inputs, in time to successfully complete. (powerup-gaming.com)
First, boot your device into the recovery mode using its device - specific button combination, which you can find online. (howtogeek.com)
Certain animals require specific button presses to defeat, and the music can change up unexpectedly during each stage, creating new challenges. (indiegames.com)