A pay credit is the yearly addition to your cash balance account set by the plan's formula. It can be a flat dollar amount or a percentage of pay. One-person plans often use a flat amount sized to keep the account close to the most the 415(b) limit allows, since a percentage of pay moves whenever salary does and is capped by the compensation limit.
The 415(b) limit phases in over ten years of participation, so each year can add at most a tenth of the $290,000 yearly benefit, or $29,000 of annual income at retirement. Pay credits are sized to stay within that.
The pay credit is not the same as the contribution. The pay credit is what the plan adds to your account. The contribution is what the business pays into the trust to fund it, within a range the actuary sets each year. The two are related but rarely equal, because the contribution also depends on segment rates, investment returns and how well funded the plan already is.
Pay credits also set a floor. Under the preservation of capital rule, the benefit paid out can never be less than the total of all pay credits made to your account, whatever the interest credits did. See what is a cash balance plan.