A lean bulk is a muscle-building phase with a small calorie surplus, aimed at adding muscle while gaining as little fat as possible. Its opposite is the dirty bulk, where you eat far more than you burn without much of a plan.
Muscle grows slowly. Energy beyond what your body needs to build it mostly ends up in fat tissue, so a bigger surplus mainly puts more weight on the scale, not more muscle. Every kilogram of fat you gain while bulking has to come off again in your next cut.
How big the surplus should be
A review on off-season nutrition for bodybuilders (Iraki et al. 2019) suggests roughly 10 to 20 percent above maintenance for beginners and intermediates, and closer to 5 to 10 percent for advanced lifters. Your trend weight should rise by about 0.25 to 0.5 percent of body weight per week.
Example: At 80 kg body weight and 2,800 kcal maintenance, a rate of 0.25 percent per week means about 0.2 kg and a surplus of roughly 220 kcal a day, so around 3,020 kcal. These numbers are a worked example, not a target for you.
Steer by the trend
Your starting number is only an estimate, because maintenance itself is an estimate. Whether your surplus fits only shows in the slope of your trend weight after two to three weeks. If the trend climbs faster than planned, eat a little less; if it stays flat, add a little.