I don't have enough context to determine exactly who 'garp' is. It could be a newly created character by the fanfic writer, or it might be a character from a relatively unknown story that is being incorporated into the 'ace fanfic'.
Fan Xian's strength was around the eighth rank. Although he had won the battle with Cheng Jushu easily, he had not surpassed the level of the Eighth Stage. In the battle before Fan Xian and Teng Zijing joined forces to deal with Cheng Jushu, his strength had increased. He also said that after that battle, his zhenqi had gone up another level. Fan Xian's hearing had not reached the level of the ninth-level ace Yan Xiaoyi, so he could deduce that his strength should be between the eighth and ninth-level. However, the specific level of the expert was not explicitly mentioned.
Fan Xian's strength was between the eighth and ninth ranks. Some documents believed that his strength had reached the Eighth Stage in Northern Qi, but he was no match for the ninth-level experts Yan Xiaoyi and Friar He. In addition, Fan Xian had won easily against Cheng Jushu, but he had not surpassed the eighth rank. However, after this battle, Fan Xian's strength had increased. Thus, it could be inferred that Fan Xian's strength should be between the eighth and ninth ranks.
Fan Xian's strength was above the eighth rank, but it was not explicitly mentioned whether he was eighth or ninth rank. Fan Xian's strength in Northern Qi should have reached the eighth level, but he was no match for the ninth-level aces Yan Xiaoyi and Friar He. When Fan Xian had first entered the eighth rank, he had almost been killed. Later, after experiencing many assassinations, his strength had improved. Combining this information, one could deduce that Fan Xian's strength was between the eighth and ninth ranks.