Not able to save sbox_maxsents to server.cfg

Could anyone help or tell me why i cannot add sbox_maxsents to the server.cfg, because whenever i do and i restart the server when its save on the server.cfg it wont load it it would just remain at 0.

Here’s my list for the sbox_max items:
sbox_maxprops 85
sbox_maxragdolls 0
sbox_maxnpcs 0
sbox_maxballoons 0
sbox_maxsents 20 <---- Theres the max sents.
sbox_maxeffects 1
sbox_maxdynamite 0
sbox_maxlamps 5
sbox_maxthrusters 10
sbox_maxwheels 6
sbox_maxhoverballs 6
sbox_maxvehicles 2
sbox_maxbuttons 15
sbox_maxemitters 2
sbox_maxspawners 3
sbox_maxturrets 0