What does "Split" label mean on circuit breaker panel?
Friedo's answer is essentially correct regarding the multi wire branch circuit except if these are 15 amp circuits they could not be used to feed the kitchen receptacles. Those are required to be 20 amp circuits.

The code requires multi-wire branch circuits to be fed with either a multi-pole breaker or two breakers tied together with an approved handle tie. You appear to have the latter. 

I just wanted to clear up a misconception many people have about how to calculate the total load of your panel.
You said-


  I have three sets of these, which would make a total of 90 amps. Quite a bit considering the house only has 250 amp service


We don't add all the breakers up to determine the load on the panel. The main panel is required to be sized large enough to supply the calculated load of the house not the sum of the installed circuit breakers.

(If you had a 200 amp panel (the normal maximum size for a residential service) with 40 breakers installed and they were all 20 amp breakers that would total 800 amps. Far exceeding the maximum of the main breaker. If the breakers were 15 amp breakers it would still add up to 600 amps.)

A residential load calculation is a fairly involved calculation but even an all-electric house of average size wouldn't normally exceed 150 amps so a 200 amp panel is plenty of capacity.

So your breakers are good. It is a safe installation according to the National Electrical Code and a normal practice in electrical installations.

Happy Day!