Problema na hora de receber um retorno int

Olá pessoal.

Estou com um problema na hora de pegar o return de uma função, alguém consegue me ajudar?

<?php

namespace App\Services\Reports;

use App\Helpers\IsUuid;
use App\Models\Subject;
use App\Models\ActivityLog;
use Illuminate\Database\Eloquent\Collection;
use Illuminate\Database\Eloquent\Model;

class CommunityStatusService
{
    public function getRegularity(string $classId, int $cycleIs): ?Collection
    {
        if (!IsUuid::isValidUuid($classId)) {
            return null;
        }

         $subjectData = Subject::query()
            ->with([
                'subareas' => fn($query) => $query
                    ->join('subarea_classes', 'subarea_classes.subarea_id', '=', 'subareas.id')
                    ->with([
                        'activities' => fn($query) => $query
                            ->withCount([
                                'activityStudent' => fn($query) => $query->where('already_know', true)
                            ])
                            ->withCount([
                                'timer' => fn($query) => $query->where('timers.concluded_at', '<>', null)
                            ])
                            ->where('activities.is_exam', false)
                    ])
                    ->where('subarea_classes.cycle_is', $cycleIs)
                    ->where('subarea_classes.class_id', $classId)
                    ->where('subarea_classes.active', true)
                    ->orderBy('subarea_classes.cycle_is')
                    ->orderBy('subarea_classes.week_is')
            ])
            ->orderBy('subjects.name')
            ->get();

            //return $subjectData;
            return $this->getTotalActivities($subjectData);
    }



    private function getTotalActivities($subjectData): int
    {
        $total = 0;
        $totalAlreadyKnowOrConcludedAt = 0;

        foreach ($subjectData as $subject) {
            foreach ($subject->subareas as $item) {
                $total += $item['activities_count'];
                foreach ($item->activities as $activity) {
                    if ($activity['activity_student_count'] > 0 || $activity['timer_count'] > 0 ) {
                        $totalAlreadyKnowOrConcludedAt += 1;
                    }
                }
            }
        }

        return $total;
    }


}

Utilizando o Insomnia, ao testar a rota, ele da o seguinte erro:

"message": "Return value of App\Services\Reports\CommunityStatusService::getRegularity() must be an instance of Illuminate\Database\Eloquent\Collection or null, int returned"