My own understanding from my end of this is that is your basel rate is correct that you can go low or high during the course of the day depending on what you are doing but that it shouldn't be that much of a spike over all - as in if your set to be at 5 most of the time then spiking to 7 or hitting 4 over the course of the day is within allowable base range between meals. Base doesn't cover meals it sits in the background at what ever your base number should be at and you need to then correct to base with your bolus amount adjusting for that carbs and protein in the meal.
Example ... pre dinner = 6, correction ratio is 2.65 off of 5 = no correction for pre meal number
carb count = 83 carbs with a correction of 1:10 meaning taking 8 units to cover carbs
protein count = 42 grams with a correction of 1:10 meaning taking 2 units to cover protein
total correction to cover meal would be 10 units of fast acting insulin
post meal = 5.5 so close to target since at the 3 hour mark I did hit 5.
Now this isn't standard and the above is what has been worked out for myself with the help of my endocrinologist and medical team, a lot of people don't cover the protein in a meal because it is a slow spike, but it can and does spike you thus we've learned that it does need to be taken into account for a correction dosage (in my case at least, can't speak for anyone else).
The numbers for me where found though a lot of trial error and money (as in having to go though more test strips in a month to figure out what was going on with my numbers after each meal), but its served me rather well over the years though now we're back to learning things again because I've had to cut a few things out that I was eating on occasion (cutting the gluten has meant a lot of the testing I did needs to be dun again to find the new happy medium, though from my own numbers we're not to far off the ratio, for dinner and breakfast its lunch that is the wild card).
