The config in this repo is using 2x schedule:
https://github.com/jbwang1997/CrossKD/blob/master/configs/crosskd/crosskd_r50_retinanet_r101_fpn_2x_coco.py

But the paper is not clear:

Besides performing CrossKD on GFL, we select three commonly used detectors, i.e., RetinaNet [32], FCOS [49], and ATSS [61], to investigate the effectiveness of CrossKD. We strictly follow the student settings for training and reference the teacher and student results from the MMDetection model zoo. The results are presented in Tab. 8.