This :
8b9ee9dd-7485-4377-94cf-6d9dcf35c229-image.png
is the Let'senscrypt' intermediate certificat, not the certificate you received from Letsenscrypt.
When you inspect the sit's (pfSense) cert with a normal browser like FF, you'll see the 3 of them :
0ebbb6d7-b950-415a-9e97-965374ce960b-image.png
Yours is the most left one.
Like mine : 4096 ....
But hey, even 2048 will do for decades ...... although you have to trach it after 90 days max.
edit : also .... the details of the cert you showed last for some 15 months .... that's not the 90 days max duration Letsencrypt is advertising with ;)