Big difference between ad requests and ad impressions

Hello , I have a big difference between ad request number (162654) and impressions (59884) in admob, is this normal and legal ? Please write down your ad request and impression number .

You either have a low fill rate or you load your ads in advance and don’t always get to show them.
If you are in the second case, you are like me : I have around 2 x more requests than impressions because my code is crap and I never bothered to change it. Maybe load the ad a few seconds before showing it (if you can know beforehand).

Thanks , I, m in the second case … I try to make the requset ad directly before showing or a few sevonds between request and show but it dosent show …
The request take more than one minute to be able showing ads … sorry for my english