My husbands pulse ox jumps around

So my husband who is 30, just had a check up annual of course and the doctor said he was healthy. I noticed on his vitals his pulse ox was 96. So I worried and bought a at home pulse ox. When taking readings his pulse ox will be at 96 then dropped at one point to 92 (we were riding in the truck talking) then back up to 95 where it stayed. He says he doesn’t feel short of breath and he isn’t blue and fingernails look good but I’m worried to death. I took it again today and it was 94 after he got done cleaning his truck and then between 94-96 then it rested again at 95. I just bought this pulse ox today it’s brand new from Walmart.