Yes, it does. The Kirkman product targeting children is designed to deliver 100mg/ gram of cream.

It is unclear to me how much would be absorbed from the lotions we are discussing. They do not give concentration values on their labels.

So I have suggested in this thread and others that if you decide to use the lotion every day on large areas, or in large amounts to cut back on oral supplements. In a normal person with normal kidney functions, magnesium in excess can be excreted easily.
In small children or the elderly this is not as likely. Most of the poisonings with children or elderly come from over use of magnesium containing laxatives and enemas.

When you swallow a mineral like magnesium, it is going to go into the blood stream and be sent all over. When you apply it topically, it will enter where you applied it, and slowly make its way to other sites. This would be slower IMO and depend on the circulation of the area you applied it. The GI tract is designed to allow things into the body more efficiently than topical application. Much of the magnesium applied topically may be utilized right there, and not make it to the general circulation.
Magnesium is used in hundreds of metabolic enzyme systems and will be taken up everywhere.

We see certain therapeutic things made into transdermal creams for local application. Knees, joints, etc. These have drugs in them that get to the local site in higher concentration than they would if taken orally. But they do disseminate finally into the body itself, as evidenced by the toxicity of diclofenac in topical RX products, getting to the liver and causing damage there.

Topical success in reaching the blood stream depends on the vehicle delivering the magnesium. Soaking in water would be less efficient, than a transdermal cream which carries the magnesium "deeper".

Basically I think if one were to use the lotions, you could give up the oral forms instead. As far as toxicity potential existing, that is unclear. People have died using Ben Gay (a young woman recently) who abused this cream and it interacted with her poor kidney functions. But I believe I read that only 12 people in 50 yrs have had problems like this with Ben Gay.

Again, people with normal kidney functions don't need to worry about the magnesium in the lotions IMO. However, people with poor or damaged kidneys, should consult a doctor before using lotions in large amounts...to make sure their bodies can handle it.