If the losses carried forward from earlier years exceed the 2021 to 2022 profit, then the balance of unused losses is carried forward to set against future profits.
If next year there is a loss, then those lossess are added to the losses carrief forward and set against a future tax year.
Box 29 would allow you to utilise the losses carried forward and set them against profits in 2021 to 2022 and box 35 would show the revised losses to be carried forward. Losses can be carried forward indefinitely.
Have a look at some guidance on losses at HS227.
Relief for trading losses (Self Assessment helpsheet HS227)