PBO and Total Pension Cost

I just found two formula in the notes which are quite similar with each other.

  1. Total periodic pension cost = current service cost + interest cost +/- actuarial losses/gains due to changes in assumptions affecting PBO + prior service cost - ACTUAL RETURN ON PLAN ASSETS

  2. PBO at the beginning of the year + service cost + interest cost + past service cost +/- actuarial losses/gains during the year - BENEFITS PAID = PBO at the end of the year.

The only difference between the two formulars I see is the “Benefits paid” and “Actual Return on plan assets”. Does it mean if the “benefits paid” and the “actual return on plan assets” are the same, PBO will be equal to Total Pension Cost? Thanks!