betterment

[highet]

does the concept of betterment exist when returning a lease car - volvo picked up this morning - on inspection everything inc alloys fine bar 2 tiny nicks about size of fingernail on side wall of 2 of the tyres - quite literally about 0.5 cm across and he was able to lift a tiny flap of rubber as penetrated about 1mm into wall - not a cut or bulge or deformation and he agreed wasnt unsafe or mot failure and happy to drive car away but had to ''note it down'' - fully expect to get a bill for 2 new tyres - had there not been sidewall nicks the tyres were down to just over 2mm tread so would need changed anyway - i know as a landlord if my tenant damages a 5 year old carpet i cant fit a new one and expect them to pay but am only entitled to charge them for value of old carpet ie no betterment - should i expect to have to pay for 2 new tyres or the value of the 2 ''damaged'' being returned ??? have already checked the leasing agreement and nothing there !!
i know when making previous car insurance claim when tyre was damaged i had to pay the difference in cost between new tyre and value of older damaged tyre!!