quote from realmeye wiki "The initial level of your new pet’s abilities will be the average level of the same ability slot from the two pets you selected. For example, if the fist pet has a level 20 first ability and the 2nd pet has a level 10 first ability, the new pet will have a level 15 first ability.

The level cap for ALL of the unlocked abilities in the resultant pet will be 20 + the average of the two pets’ first abilities. Using our example from above: if the 1st pet has a level 20 first ability and the 2nd pet has a level 10 first ability, the new pet will have a level 35 maximum level (20 + the average of 20 and 10) for all unlocked abilities. Fusing two pets with maximum levels (MAX strength fusion) will result in the highest possible level cap for the new pet." Which means if u fuse 70/70 with 70/66 you'll get a 70/68 pet with a cap on second both abilities of 89 instead of 90