I have been tracking the usage for our two cell phones. Until recently, the 250mB limit had not been reached. That's not my issue though! Now I have been checking it daily and find that the Usage page gives me one number ie., today for example, 203mB but when I check the individual daily records, they are each consistently 20mB less. EVERY SINGLE DAY, THROUGHOUT THE DAY. I did call customer support but was told that there must be a data block waiting to be posted. Told her that this has been an ongoing discrepancy. She said that she would get back to me (she didn't). I can understand a delay in posting but when the number is always 20mB on each device, I have to call BS.
There was a discussion elsewhere describing a data RESERVE that is made to an account. That there is a 20MB consistently on your account would support this surmise. It also gives a bit of headroom to get a notification to you as you approach any limits you may have requested notifications for.
There is a 20-80mb delay for up 6 hours depending on what you were using the data for ie: web browsing, streaming etc. The notifications come in a timely manner, so if you get a text at 90% you are at 90% at that time, but you may not see the exact usage in telus.com for up to 6 hours. If you are repeatedly looking all day every day as you say, then it is going to be confusing all day especially if you are adding up to the mb. The summary of both lines is the most accurate. The single line is going to be what's most delayed as that is what we are trying to give you the most accurate information for. If you are getting this close to your data consistently, it might be worth the $10 extra to just bump it up to 1gb. Depending on your tenure the loyalty department may be able to do something for you.