Gabapentin and Trazadone dosage and instructions

My vet has prescribed my dog gabapentin and trazadone for calming meds. I usually give it to him before nail trims, vet appointments and tech appointments for cytopoint. He’s not aggressive, he’s just a grumbler and a very strong and muscular 108lbs. The instructions say to give 2 300MG Gabapentin and 2.5 100MG trazadone the night before an appointment and again 2 hours before the appointment. I didn’t realize the “night before” instruction until recently when a tech told me I was supposed to and then it was added to the bottle. I give him this dose 3-4 hours before his appointment and he is usually completely out of it in time for his appointment and for the next 24 hours. I feel awful doing it because he just seems so confused and tired, but he’s much easier to work with when he’s kinda lunked out. When he was younger, I feel like this dose made more sense because he was kind of wild as a puppy. He’ll be 5 in a few weeks and he’s much more very mellow now. I feel like this may be too strong. He has a nail trim at noon and I gave him 600MG gabapentin and just 200MG Trazadone around 8am. Do you think it’s okay I gave him 50MG less than the prescribed dose or should I give him the additional 1/2 pill? It’s been just about an hour and a half and the meds are kicking in for sure. He’s a boxer/Amstaf/Pitty mix.