I got a Temp question

[bleu]

I have an old Brower incubator and the thermometer looks like this. My question is why is there printed arrows around the 103 marks. The marks around the 99 were drawn on by somebody. Just wondering

 

[Tuffoldhen]

My thoughts would be the arrows at the 103 mark are the highest you could let the temps get and the 98 would be the lowest.....I would think the person was trying to keep everything in that range limit since its an older incubator...and a way to spot trouble...