There is no issue. Both learned and learnt are acceptable and attested for the verb, pace the OED: learn, v. Forms: Pa. tense and pple. learned /lɜːnd

There is no issue. Both learned and learnt are acceptable and attested for the verb, pace the OED: learn, v. Forms: Pa. tense and pple. learned /lɜːnd/ , learnt /lɜːnt/ .