can i use 30vol developer on my roots?

i bought 30 volume developer instead of 20 last time i went to sally's, for whatever reason (🤦). i don't feel like spending the money to get another bottle of developer, is it stupid to use the 30vol to lighten my (~1 inch) grown-out roots??

whats the difference between using 30vol for like 15 minutes & 20vol for like 30 minutes??

also i will be using ion absolute perfection step 1 with it to lessen damage !!!